Shinjuku 18

Hmm, interesting. I felt the fight was easier than 17-2 which I ended up using my command seals cause I didn't feel like loosing the ap.
Have you been killing Archer first? My team comp was Li Shuwen, Vlad Extra, Waver with a Combat suit Waver. I knocked out Archer of Shinjuku with Li Shuwen and Vlad then used the remaining power for Enigma. I ended up losing Vlad Extra but my extra waver came in and with the buff for the final fight, ended up np spamming the thing to death.

My team are Jalter Lilly (Black Grail CE)-Mash-Merlin-Leonidas(Batlle of Camlann CE)-Kiyohime(Just in case Lily died) with combat suit mystic code.
When Archer use NP i always use mash invincibility+target focus/swap leonidas&use target focus to keep main team alive.
Note : Maxed Skill Jalter Lily&Mash (10/10/10)

Used Merlin + Scathach + Waver. Scathach has anti-undead and stun in np. Stop Enigma from doing anything, kill it then focus on Archer.

No CS or quartz used. my team consisted of Merlin, Karna(Kscope), Sanzang(MLB Heavens Feel), Enkidu, cu chulainn, and mash. I used immediate NP for all three front line servants built NP back up rinse and repeat. The only servant I lost was Karna. Enkidu came in and finished the job with Enuma Elish.

Borrow someone Hercules with Bond CEs or Chu Alter and put one of them on your backline for safety. I'm focusing on raising my evil servants Bond Point and FP as well, so no Waver nor Merlin for me.

I have quite the experience myself of clearing Camelot by using 1-3 stars servants and sheer tactics and experience alone, i hope this information can be a little help for you and here you go.
It's quite hard to beat it by using 1-3 stars, but it's still doable and i want to save SQ too so here's my party : Emiya Alter ( guess servant, Friend Point + 200 ) + Mashu ( Little Halloween Devil ) + Ibaraki ( Golden Sumo ) + Jalter Santa Loli ( Holy Night Supper ) + Caesar ( Chaldea Lunchtime ) + Hercules ( Bond CEs ) and No command spell.

- Stage mechanics, that Avenger beast can remove all of your buff before he kill one of your servants if his NP bar already reach the 5th gauge. However, i see a weakness there because all of the Bosses there can be debuffed.

- Moriarty and the beast itself have a good hitcount, it's also a weakness for them. high hit count = faster NP gain = can use NP more often.

- double or triple tank can ensure you to use a hard hitting Zerker like Kintoki or Raikou so the battle will be shorter. The basic one is Mashu and Georgios, easy to raise and the best tank yet on FGO.

- if Offensive methods are failing, consider to use more safety measures like equipping all of your servants with survivability CEs and play more defensifely.

Bonus : my tactics, i wait and fill Jalter loli NP bar to 100 % with her all cards on the screen then swap Emiya Alter with Caesar. Moriarty health is reduced to his last bar because Caesar is Caesar and Jalter Loli herself is NP 5.
At this point, i'm focusing on bringing down Moriarty ASAP because he can use his NP pretty often and it's freaking devastating to my team members.

Mashu is already dead because she already tank attack from the beast, Ibaraki came in to help me finish Moriarty.
Jalter Loli, Caesar and Emiya Alter is also dead because the beast can Crit pretty often, i don't bring my debuffer and of course my DPS tank the beast NP head on ( beast boss buff removal + ST NP is a nightmare ). Make sure all of your party members were killed by one of the boss before your last man standing is coming out from the backbench, Hercules or Chu Alter alone can make it easier.
The beast of Shinjuku B*el pretty much still have it's HP around 40-50 % left, this time my Hercules will finish the job and bring me victory.

I'm not reading any walkthrough and pretty much i'm failing each node with bosses such as doggo or Moriarty one time or two ( doing blind run and i don't know any of their gimmicks ).

Hard to make recommendations without a little more information on who you have, but I'll try to make general recommendations.
My frontline was Scathach, Merlin, and Mash. My support was a grailed maxed out Euryale in the 4th slot. Last two were Evil-trait Servants I decided to bring along for the Bond point bonus.
Mystic Code was Atlas Academy.
Scathach is perfect for taking out Enigma, since her Third skill increases dmg against Divine and Undead, which Enigma is both, and her NP has a guarenteed stun, so thats a plus. She also holds class advantage over Moriarty, so she is a perfect fit.
Euryale (preferably a Grailed, 10/10/10) with MLB Black Grail, is incredibly good for nuking Moriarty. Despite not having class advantage, her double NP dmg takes out a HUGE chunk out of each HP bar, and it only takes a few turns to charge it up again, especially if you can pull off an Arts chain.
No matter the lineup, you're going to need to prepare for a long grind, so having 2 Support servants is a must, preferably Merlin and Mash and a third offensive servant.
Atlas Academy Mystic Code is pretty much essential, as it has a single target invincibility, and can reduce the skill cooldowns of one Servant by 2 turns, so in tandem with Merlin and Mash, you've pretty much got Invincibility on demand for whenever they can pull off an NP (sans for surprise ones), assuming all their skills are maxed out.
Scathach, Euryale, and Tamamo Lancer are great picks to round out the frontline. The boss guide here on Gamepress also contains a list of other Servants that work well, as well as videos of several team compositions that completed the level.
I'd offer more advice, but without having a better idea of who you have and what Supports you have access to, there isn't much else I can really recommend. I'll edit my answer if you update the question information.

I started with Merlin-JAlter-friend's Waver. JAlter (10/10/10 Holy Night Supper CE) killed Enigma pretty quickly twice. Then when Archer of Shinjuku was using his NP for n-th time, and Merlin's skill was on cooldown, I switched Waver for Mash. A couple of turns later JAlter was killed by a sudden NP, and her place was taken by smol Santa JAlter to finish our gentleman in two turns. All that stuff happened in under 20 turns overall. No CSs used. Chaldea Combat Uniform mystic code.

Since I'm a F2P with not so "high" luck, I defeated him while using a team with Mash (CE: Iron-Willed Training)+ Jalter (CE: Holy Night Supper) + Merlin (Support) at the frontline and my backline are Nero Bride (CE: A Fragment of 2030) + Medusa (Lancer) (CE: Halloween Arrangement) + Kiyohime (Lancer) (CE: Joint Recital)

I killed Enigma first cause he's really annoying, and then just kill Moriarty. When Mash and Merlin are out of invincibility skill, I switched Mash/ Merlin with Medusa to tank his NP because she has the Halloween Arrangement and a 1 time invincibility + a 3 turns gut also her kit have a charm and a stun so it's kinda good. And only thing left is rng

Personally, I went with a frontline of Mash, Nursery Rhyme, and Merlin (support). My idea was to deal decent damage and mitigation while stalling any NPs from the enemy. With this, you'd want some kind of np gain on Nursery or other draining NP (I rolled a heavy amount for MHX Alter, so I have a MLB Cute Orangette) and focus down the enigma. I put a Prisma Cosmos on Mash, but thinking about it, if you have a Melty Sweetheart that may work out better, since AoS only hits once per turn while Enigma is up (or am I getting that mixed up with the previous battle?). Requires a decent amount of luck for the charge drain, but the comp got me through on my first try, without any seals. Enigma got off one NP before dying. Most worrisome part is the drain only hitting one or Archer's charge skill before Enigma dies: then you can't cover both NPs under Merlin's illusion. As for the backline, servants suited for Archer himself are good choices, so stuff like Euryale, Tamamo Lancer, Cu, Heracles... Anyway, yeah, stalled out their NPs, killed Enigma, and then only used defensive skills to make sure Archer killed solely through his NP and wore him down. Hardest part was Archer using his charge skill twice in a row, and letting loose (bastard). Oh yeah, I used the Chaldea Mystic Code for this, giving me a few heals and evasions with the relatively low cooldowns.

Almost forgot to mention, the biggest problem with this comp might be the time necessary to get the NPs rolling. Just using Dreamlike Charisma and Meanwhile may not be enough, so don't hesitate to use Shield of Rousing Resolution and Obscurant Wall of Chalk for the np gain, as you'll be planning on shielding the first set of NPs through Illusion anyways.

I wish I had time to read all these before work but it'll have to wait till after. I used Mama Raiku(HNS) + Merlin(2030) + Merlin(Lunchtime) + TamaLancer(Joint Recital).
I'm not sure if you have your own Merlin to use but double Merlin's stay undefeated. I brought Mama for buster crit and evil damage. She broke ghost bro turn one and came a couple thousand from finishing him on turn 2.
Then I just had to wait for her to die and the fight would wrap up shortly after thanks to TamaLancer's anti male. We took him out in 7 or 8 turns rotating Merlin invincibility to beat his NP. Also using Atlas suit to lower skill charge for a Merlin.

Like someone said that I did read, it is a little hard to make suggestions off what was provided. Sometimes too just keeping it simple is a good way to approach things.

For me I had Jeanne d'Arc Cu Chulainn (Alter) and Merlin I was able to take out enigma first before cu died then after 30 turns slowly killing archer and blocking his np with Jeanne np and giving health with Merlin np he cant kill you faster than you can spam

That's really interesting after reading your post and all the comments I just used all lancers x'D and Mash and I won.
Jeanne with halloween princess, 2/6/4, np 5
Mash (not max lvl) with lil halloween, 4,4,4, np 3
Cu proto (lv 60 btw damn twins keep avoiding me so i can't ascend him!) fondant au chocolate, 2,5,5, np 5
Elisabeth, sweet crystal, 6,5,4, np 2
Cu, holy night, 5,8,5, np 3 (cu came in clutch, last man standing).
support Scath. knights of marines, 6,7,6, np 1 (stun gave me the fighting chance, fought valiantly).

Using Merlin, my cu alter with kscope and a support Tamamo lancer with kscope that was grailed and max skilled, I used cu alter noble phantasm twice in the first 3 rounds on enigma and then Tamamo lancer casually slapped around Archers nuts. With her feet.
Didn't use backline and found the fight significantly easier than the previous fight.
Also mystic code was the one with the the +20np charge to selected servant.

I was able to beat it without any C-Spells or quartz with the following comp:

Lvl 66 Mash (10/4/3, Valentines Shop CE)
Lvl 90 MHXA (2/2/4, Cute Orangette)
Lvl 90 Merlin (10/10/10, Ox-Demon King, Support)
Lvl 55 Hans (1/2/1, Imaginary Element, NP4)
Lvl 55 Leonidas (3/1/0, Shroud of Magdalene/[Grand New Year should work well too], NP3
Lvl 70 EMIYA (1/6/4, Necromancy)

My plan was to nuke down Enigma with MHXA while rotating merlin's invul with mash's taunt in order to deal with the enemy NP's. Once Enigma is down, I swapped out MHXA for Leonidas to create a pseudo stall team (I did make a mistake here since I swapped in leonidas to taunt Archer's NP without invul or guts, in hindsight, should have equipped Grand New Year instead of Magdalene). When Leonidas dies, the resulting mash-hans-merlin team will also be somewhat decent at stalling further and should provide a lot of sustain. Eventually, one of the team WILL fall to the enemy NP, but the remaining DPS should be enough to clean up with team support, as the team comp more or less still makes sense until the end.

Also: don't hesitate to use Merlin's 3rd skill for hp/during stall situations. One of the highlights during my run was merlin taking out about one thirds to one half of archer's break bar by himself, using a boosted BAA chain.

TLDR: With the servants you mentioned you should probably be able to beat it cleanly. Try setting up a team comp that's resistant to mess-ups/sudden crits/unplanned deaths, and proper skill usage with some luck should help you clear it.