Bottomless Mags and COV weapons don’t synergize very good, as only the ammo pool regens and heat is almost unaffected. This means that you have to repair your overheated weapons all the time and its also very hard to keep up an anointed mag bonus.
Regarding builds it mostly comes down to which weapon you want to use. These are my most liked Bottomless Mags build weapons:
These Torgue assault rifles with alien barrel fire like a flame thrower and increase in damage the longer you fire them. They can do insane damage and the ammo consumption is low enough to keep firing for a long time.
Big mag size coupled with ammo regen lets you fire them forever. Try to get a Super Shredifier for double barrel action, but Bipods can also be good long distance crit spot shooting. This thing benefits the most from “Click, Click” as it is very easy to keep it at a sweet spot for the most effect.
Not as strong as the Blister, but can also perform very good. The low ammo consumption rate helps keep this thing firing for a long time.
The natural ammo regen on the Butcher makes this possible. Just add more mag size bonuses. Keep in mind that grenade and shield can also be Hyperion, which boosts Matched Set to +60% mag size bonus.
Try to get a version with 22-24 mag size and then stack all the mag size bonuses you can find (Matched Set, Iron Bank, +40% artifact). This can bring it to a mag size of 50 which is very manageable on a Bottomless Mags build.
Sorry no skill tree as the skill trees are down at the moment on the borderlands page.