1-3* team compositions

Medea, Robin and Hans can make a decent arts team, although they may be lacking in damage for bigger waves since their NPs and skillsets compliment taking down single targets.

Hans is a great support that can fit into most teams with his NP buffs and star gen, so he'll probably be more beneficial with crit teams. With your servants, I can see him being paired with Hassan and Cu.

Lubu is better fitted for buster teams. So unless you have other berserkers/buster oriented servants, I can't really recommend putting him in a team unless he has the proper supports to help sustain his damage and survivability. Technically Mash can help with that, but she is very lacking in damage.

Actually, Lu Bu is better of with Leonidas than Georgios, so:
Leonidas + Lu Bu + Shakespeare/Hans. Leonidas is perfect for him. Buster Lancer, he can keep Lu Bu alive, generate stars that can be used for Lu Bu's 3rd skill. Shakespeare is there to give more burst damage to Lu Bu, but can also be switched to Hans for more survivability.

Robin/Euryale + Mozart/Hans/Mash/Georgios (pick two, but don't bring Mash and Georgios together). Take note that Euryale is strictly for male opponents. I listed Mozart since he can help with Robin and Euryale's burst damage better than Hans, while Hans contributes to a more stable damage output and survivability

Cu is a backliner, don't bother with team comp, unless we are talking about Proto Cu or Cu Caster

Medea is quite flexible. Ideally, she should go with art team, either as DPS or support. I can't really decide what's the best team comp for her since she does really well on any team that has a good number of art cards and even with the lack of art cards, she can still hold her ground well.

Georgios and Hans fits a lot of team comps easily since they are arguably the best 2* in the whole game, and they are easily one of the best supports you can get. Though, there are cases that you'd better off without them (like Lu Bu's case with Georgios, like I already stated before, he is better off with Leonidas), but those cases would be pretty rare.

Hassan, is a stargen and if you can provide him stars he can work as a NP spammer, but at this point, we don't really have the access to the latter, so, he is limited to star generation.