Which Servants to Lvl Up.

Saber: Altria Alter Saber or Sigfield, pick one. Raise Raman or Eliz (I prefer Rama)
Archer: Emiya if you plan to build a critical team for him
Lancer: Just no Fionn
Rider: Santa Alter oc. (Altria Alter Rider normally means another SSR Maid Alter)
Caster: you are really lacking of caster support? Raise Helena immediately. Then Liz
Assassin: depends. Both are good and solid for tough challenge quest. Camilla is for np2 and better np gain, but Kiritsugu has really good star generation and 3rd skill really helpful
Berserker: Lancelot>=Banana

So ideally you'll want at least 1 Single target and one aoe of each class. Caster might be the exception in that you want a support.

Saber- Saber Alter is good, Nero is eh. Siegfried is alright, but he's more geared toward dragons. This is just based on skills however, I've only used them each a few times. I'd say Rama is better than Brave Eli. His bonus damage can come in handy and his skills are nicer (Eli's 3rd skill is basically useless).

Archer- I'd do Emiya for the aoe since you have Archturia leveled. Summer Anne and Mary are single target, though they have an interesting mechanic.

Lancer- I haven't used Fion much, but based on skills i'd say Santa Lily. You might want a second opinion on that though.

Rider- Santa Alter is basically better in every way.

Assassin- I'd say Carmilla. She'll be useful in Babylon, and you have her at np 2. Her bonus damage is nice and she is one of the best 4 star servants. She also has more utility than Emiya.

Caster- Helena has support qualities that are nice. Caster Eli is more geared towards farming and useful in some events. I'd do Helena first.

Berserker- Lancelot is supposed to be great for Babylon since he has neither good or evil alignment. His quick np is less of an issue since he's a berserker. Tamamo Cat is ok but her stun on her np is kinda annoying. Ibaraki is single target so add her to the list. Her skills are also decent.

I can make a good case for any of your sabers. Choose the one you feel works best for you.
Emiya works a bit better especially with np2. Raise 2 3 skills.
Jeanne alter lancer. Raise her 3rd skill and use her as a buster dps.
Salter. Will kill everything. Raise her 3rd skill
Helena. Skills 1 and 3.
Carmilla. Better damage especially at np2. She is more about her cards than skills, so level up the ones you need.
Lancelot if you are confident in stargen and keeping him alive. Ibaraki otherwise.