team building

Nero Mash Waver seems like a pretty good arts team to me. If you're going arts tho you can always try to summon Tamamo

Always use class advantage first, then raise your servant for support, tank, dps AOE ( farming and large hp mooks killer), ST (Boss killer), Last man standing and your waifus/favorite of course, cause FGO can be beaten with just 1-3 stars servant. That's it in general.
You can also play it in your way and there's so much team composition out there.
" Your team, your game, your dream "

Because your servants have high cost, i highly suggest investing in low cost servants, especially for events with 5 star craft essences. With 5 5star ce, 60 cost is already gone from your limit of 111. So 51 left. You have 3 5 star servants which use 48 cost. So you can only have a 1 star servant. Most likely, you won't use karna and nero bride together, leaving you with 19 cost for 2 servant positions. That is a 4 star and 3 star or 5 star 1 star. Some servants to consider are: arash/spartacus for farming, mozart for arts support, hans for general support, robin hood/ any archer, ushiwakamaru for utility, medea for killing assassins. The premier list would be heracles, carmilla, ibaraki, tristan, emiya, martha, lancelot, helena, nitocris, etc.