I gear my bots as cool as it is rational to. Total gearing budget per one char is 15-20K, I get 359 and 353 cheap epics and some blues. Also, I tune their gear with top enchants/gems to make 'em looking like freshdingers. It does help them to kill mobs faster and to draw much less attention from other players.
I like to gear all mine out, but that's mostly just because I like to top DPS charts on the few occasions that my friends want to run some heroics. TBH, it's mostly just stupid e-peen.
I get good gear for mine like pvp gear or some from the ah just to make farming easier and to make it look like it's more if a player and not just a toon that is a farming bot.