Beginner help with Team Composition

Invest in ushi,Julius for strong st np and class coverage and if playing blind get a aoe support preferably berserker like Minamoto no raiko ,Emiya and Fuuma have Low Attack at that lv

Honestly, I'd say just farm the daily quests for exp and level up your servants first. Really makes a big difference.

If it's London, I'm guessing the enemies were assassins? To deal with them, you would normally use casters. As far as offensive casters go, Charles Babbage is pretty decent, but in your case, I'd say a team of Jeanne/Emiya + Fuma + Hans with Mash in the back is enough. The idea is to use everyone to generate stars (Emiya after strengthening and Fuma can do it really well with their attacks, and Jeanne and Hans both have skills that grant stars passively each turn), then use Hans to boost crit damage for Jeanne or Emiya, and keep criting enemies. Meanwhile, whenever you can, use Hans/Jeanne's NP to support the party. This won't work without higher levelled servants though, and Emiya needs his 4th ascension to be good.

If you don't feel like levelling your servants, I would say keep using what you have until you can't proceed as you are. You did say you got unlucky with the crits, so next time might not be so bad. Team comps aren't all that important, and personally, with what you have, I don't know if there are any effective team comps to deal with London without having higher levelled servants or skills.

I would definitely recommend doing at least a few daily quests each day while they are still on half cost. They only get this cost discount very rarely, and if you just started you can probably spend an entire level's worth of AP on dailies, ding again to get all your AP back, and then continue in the story with stronger servants.

Also, allow me to congratulate you for getting a 5* so soon after starting.

Not to beat a dead horse, but I would also recommend leveling your servants during the remaining half AP cost. You have good servants but you’re still so early that you don’t have a lot of synergy for strong team comps just yet. Especially lacking any of the major supports in the caster class, outside Hans. Since your in London you’ll be fighting a lot of assassins who will be able to land those stray crits more often than not.

I always keep some friend slots open for new players if you need some help there. I’ve currently got Raikou with an MLB kaleidoscope, Merlin, Musashi, an NP4 Nightengale which can make her a surprisingly effective healer with her NP. I can also add Waver for another support or Davinci, Illya or Helena if you need some offensive casters. My ID is 825,960,988 so if you want to request me let me know and I’ll be sure to add you. And if there is a particular servant you’d like me to add to my support and I have em, I’d be more than willing to try and help! Just let me know if I can help

Until you reach camelot a support berseker can carry you trough all the singularities...Just level your tanks (mash, george and leonidas) and pick either cu alter or heracles from support.
Even in Camelot most of the gimmick knights can be soloed by Heracles.
You might want to take advantage of the half ap ember to level your team tough...leave the singularities for later since they won't go anywhere.
The next event that requires you to complete singularities to participate is SERAPH in May. Try to complete Solomon until then, otherwise you will miss out on BB chan.