I mostly use Siirvend's generalist builds; they're enough for most cases. But I still can't shake the feeling of missing out on different overclocks, weapons and builds. And yet I'm not very good at coming up with something new. Part of it is being used to builds I normally use, another part is just lack of creativity lol
EDIT: Maybe I should just hit the "random build" button or try a Randoweisser
What I do is pick the thing I really want to try out, then just make guesses for a trial run. If I think I'll run out of ammo I'll equip that, for example. Then during the run, take notes of what's not going to work, like if bugs are surviving but one damage upgrade can kill them, or the reload is taking too long, etc.
TL,DR: just pick something that looks cool and fix it over time.
Generally trial and error until I get the feel I want. Set up a build one way, try it out. If I find myself running out of of ammo, not doing enough damage, etc, I'll try to remember that and adjust for next time. Although by this point I've played so much all of my guns are pretty locked in and I think I would get confused if I changed OCs now.
I did greatly enjoy the new set of OCs they released. Using most of those now.
I break it down by roles.What do I want this weapon to be for? Crowd control? Single target annihilation? Support? And then I go from there and tweak as I try it.
For example, I like to use the flamethrower when I'm playing with friends and we have to deal with big waves of fodder. To make it really good at that, I go for Sticky Flames so I can make barriers; I also maximize ammo capacity because I know I'm gonna be shooting this a lot, often preemptively, and high damage will be wasted on grunts anyway.
(granted, I would imagine that this is probably a common build for this weapon, but the logic still stands)
also, don't be afraid to try the more quirky overclocks and try to make them work! IMO this helps with the creativity part
That's how I do my gunner build. The minigun is geared for crowd control and sustained fire ability, the revolver for precision high damage. My perks and shield choices were made together to be a better medic.