Color me jealous, my wife just looks at me like I’m nuts for dumping so much time into this game. In all fairness I’m pretty nuts, so she’s not wrong.
Cruise the character specific sub forums. There are quite a few Axperts and Gunzerking Management instructors active. I don’t specialize myself, but the experts helped me a lot. The only advice that I think is really necessary is to give all of the gear a chance and not to be afraid of respawn fees. Money is easy to come by, and there are lots of hidden gems in the game.