It depends upon your desires, the rules set(s), what type of ships you have, their capabilities, and what you want to do, among others.
Line Abreast
Line Astern - Column Formation
Two-Column Formation
Echelon Left
Echelon Right
"A" Formation (or "V" formation)
"V" Formation
Diamond Formation
Those above are some of the typical formations for naval warfare. Space is 3-D, so it could be even more complex, if desired.
Modern US Carrier Groups, as well as those from WWII (and Battleships too), would frequently have the largest ship(s) in the center, and then concentric rings of others spreading outward from that. Heavies towards the interior, and lighter, "screening" vessels outside of that, kind of like the layers of an onion.
I hope that helps.
It's Sci-Fi, so don't restrict yourself to conventional norms, unless you see and advantage in it.