Bip-Bip is not the brightest bulb in the pack. He never has been, and never will be. But he is loyal to those he trusts, especially his family and his species. Unfortunately, he tends to trust too easily. He's also a literalist, a contrarian, and can be quite ornery. He's happy to serve, so long as he thinks it's his idea, but if he feels forced into something, the result is likely to be disaster -- or worse.
However, Bip-Bip has always been good at accurately throwing things, or shooting weapons. It just comes naturally. He's also naturally good at piloting and driving things, but that generally doesn't interest him so much. Shooting things is much more interesting.
Bip-Bip has a pretty simple understanding of who the bad guys are and who the good guys are. You are a bad guy, if:
1. You are a non-Gungan who treats Gungans badly.
2. You are a Human who treats non-humans badly.
3. You are a rich/powerful person who treats the poor/weak badly.
Otherwise, you're probably a good guy, and likely to be trustworthy. Generally speaking, any Imperial is likely to hit at least two of the three above criteria, so they'd be really bad guys.
Bip-Bip doesn't like bad guys. Bip-Bip likes to shoot bad guys. Bip-Bip likes to make bad guys go away and leave good guys alone.
Bip-Bip is not all that motivated by money, except in so far as it helps him get better weapons so that he can do a better job of shooting bad guys.
Ultimately, Bip-Bip has a heart of silver, if not gold.