What team can/should I build with my current servants?

Personally, I'd say your focus should be on levelling servants. Trying to get through Camelot with an average servant level of around 50 is gonna give you a real bad time. I recommend not doing it until most of your party is max levelled, but I think an average level of around 70-80 could probably do it.

A lot of your servants would go fine together tbh. With team building it's less about which specific servants would go together and more about knowing game mechanics and exploiting them. Ie, if you want to make a crit team, best not to include 2 servants with high star gather weight, or they will steal stars from each other. It's hard to come up with specific teams since most of your servants can go together fine, it's more about what specifically you want from the team.

With regard to specific team builds for Camelot, It'll be a bit difficult to get through with what you have if I'm being honest. I won't go into why at the risk of spoiling, but with what you have, the best build would be something like:

- Emiya/Euryale + Hans + Fuuma. This would be a crit team with the archer as your DPS and Hans providing most of the support. Fuuma is only there to generate stars. Emiya specifically is better for crits, but Euryale is arguably better for Camelot. Also, riders like Ushi could replace the archer DPS in that team if you are going up against casters.Fuuma could also be replaced with Cleo if you need better damage, or Cursed arm if you want better survivability. You'll also want to level Medea. An offensive caster is a good asset to have.

Another option you could try is using Georgios, CA Hassan and Mash with Cu in your backline for stalling. For this setup though you'd probably really need to level most of their skills pretty highly. For all teams though, put FSN Cu somewhere in there, usually at the back, just for emergencies.

Personally, I'd say just level your servants as high as you can, then go into things with class advantage. Usually having the right class tends to yield results similar to or better than having specific team builds with servants without class advantage. ie, if you are up against sabers, just throw Emiya, Euryale and David at the problem, and of course grab a strong archer like Orion from the friend list. Or just get Waver.

EDIT: wew lad this turned out a lot longer than I intended

Wait Wait Wait Wait Wait!!!
You have not one fully leveled Servant not even one 5-Star until the current event and made it to Camelot without a problem?

Man... Now I'm questioning myself if all the hard work and most of all the time(!!) leveling all those Servants was actually worth it.

I haven’t cleared Camelot yet but i think u should focus your investment in just 4,5 servants like zeroz said until they’re strong. And the current halloween event gives u a decent SR saber i think u should take, she can help you later on

What part of Camelot are you struggling with?

The part where people has the more problem is the Knight of the Sun. Euryale is one of the characters capable of disrupting his gimmick entirely and trivialize the fight. You can do Euryale, Hans and Tamamo/Waver (support), that should make the fight super easy.

Another popular one is the last boss fight. That fight is designed to use the NP Upgraded Mash, use the lv 90 Bedivere that the story offers you and the third slot can be whatever (damage dealer, taunter or Hans). The trick is to stack defense buff with Mash+Bedivere when the boss is about to use his NP, that way you can survive the blast and keep dealing damage till it dies. This is almost like a canon way.

You can also search for a Bond 10 Heracles friend, he can clear anything on Camelot by himself just by putting him on the last slot.

Enjoy Camelot.

I would suggest to levelling Mash first, she's really helpful in this singularity.
Then try to levelling Emiya/Euryale, it will help you to kill Gawain/Modred.
If you want to be more easy to clear camelot, try to levelling other servant, but it would take some times to make them around lv 60/70.
But if you want to get trought camelot without levelling them, i suggest you to find some friends with max levelled up servant like Jalter, Herc, Kintoki Rider/Ozy, & Jack. Then build a team around them + to make sure they're keep alive until boss fight ( Bring David/Georgious/Leonidas).

You have hans mash and georgios as supports.
Your damage is fergus, emiya/euryale, proto cu, ushi, cleo, and medea. Pick one according to the enemy team comp.
You have kojirou and hassan for stargen. Use with hans+a decent crit damage like emiya/proto cu.
Put in david as your 4th slot.
Level arash for wave clear.
Use cu as your last man.
For example, against the cu medb battle in america, you can use cleo, mash, georgios/hassan, david, cu.

I'm gonna second what zer0z said, and advise that you just focus on building up some useful servants for now.

But try to do it in a bit more of a focused manner. Like, pick one good servant of each class and level them up first. You're generally going to get further with a few max level servants than a huge variety of mid-level servants.

What I mean is, it would be much better to have a level 70 Cu, than a level 50 Cu and a level 40 Cu Proto. Just pick one (I'd recommend the original Cu), and max him out before you start worrying about a second lancer. And really, even after that, you shouldn't really worry about a second lancer until you've already got at least one servant of all the other classes maxed out.

Same with your assassins. There's no good reason for you to have 3 half-leveled assassins. Just pick one for now, and get it maxed out.

To answer your question about the best teams you could build with your current servants... For general purposes Hans + Fuuma + Emiya would probably be your best bet. You can replace Hans with a borrowed Waver, or replace Fuuma with a borrowed Jack, or replace Emiya with another DPS servant that has class advantage. But the basic structure is support + star generator + damage dealer. The damage dealer should generally have a decent natural star weight (such as an archer or a rider), or it should have some star gathering skill.