Team Composition

Use Hans to keep Tesla alive and steadily supplied with crit stars. Advised to level up Hans NP gain skill and star generation skill asap. Carmilla can help on star generation as well, and after Emiya gets his second strengthening with Hawkeye, they'll make for a nice pair of AoE Archers that'll dish out crits. Chloe and her 3rd skill will also provide a great amount of star gen.

Keep Cu, Chloe/Emiya (depending on who you picked for the front line) and Mashu on the back line when things go south. You can interchange Hans for Mashu as well, with Carmilla providing the star gen and Mashu acting out as a tank for both.

First of all, congratulations for getting your 1st SSR :)

Secondly, Nikola is an Archer so he has high star absorption but lacks the capability of making stars so Hans who can produce critical stars with Innocent Monster or someone from the assassin class like your Carmilla, Fuuma Kotarou or Hassan of the Cursed Arm can help out.

Nikola would also benefit from buffs so someone like Caesar, Ushikawamaru or William Shakespeare can boost Nikola's damage and NP gain even higher.

For mystic code, Chaldea Combat Uniform allows you to shuffle your servants around so you can bring in the stacked buffs once Nikola is ready to unleash his NP :)

Hope this helps!

Tesla, Hans, Friend's Waver (with 2030), Mashu, Shakespeare, and anyone else to fill the last slot (maybe Leonidas for more buster Boost or Cu for last man standing).
Equip your Tesla with CE that gives either buster, NP up or atk up. Atm, I personally use Sumo MLB to my 10/10/10 Tesla, as he doesn't have atk up on his 2nd skill yet, you can also give him the likes of LZO, Joint Recital, Kaleid Ruby MLB, and such depending on the fight. Later down the line, you maybe can give him Heroine Eli-Chan adventure CE from this year's Halloween (NP and buster up), or Aerial Drive (Buster up, NP Up, and NP Charged at 50%) from next year's Halloween.
As for support, I'd equip them with 2030 or any CE that gives passive star per turn to help Tesla maximize his damage.

I recommend shakespeare with taunt ce or on death effect ce. Also, david. You will be fight mostly sabers and david is great on most teams. Plus the arts cards will help build np gauge.