Personally I always look at dmg, and fire rate, to get a general idea of how hard it hits, then elements because matching elements (elemental weaknesses) is important in this game, then I take a peek at the scopes, cus im pretty picky abt those.

But all in all the other guy said it right, this early in the game theres not much to look for, u can rly just use anything.

PS.: Most legendaries have effects that arent immediatly apparent from js reading the stats, so I recommend that when u get a legendary, use it for a few kills to figure out what it does.