Some questions about making somewhat consistent builds

I picked up Dead Cells a couple of months ago and I really like it, I've advanced until 3BC but have been playing at 2BC to practice a bit. I've played a fair amount of Hades, StS, some of the build-crafting is simple when you get a dream legendary bat or similar, but I'm curious how the more experienced players improve the build as they go, I'd like to be less RNG-reliant.

I guess one question would be, what are the ways to "force" improvements? First look for a solid weapon and then reroll it? Then rerolling shops looking for synergistic support skills or shields/secondaries? Should I use the backpack to carry an item I'm rerolling but can't/shouldn't use yet because it doesn't have the right roll(s)?

Sometimes I run out of money rerolling, sometimes I don't even need money in the last 2 biomes. Are there types of items that roll or don't roll certain affixes? I also avoid the 100% damage dealt/taken rolls, but that's more of a skill/fear issue on my part. I may be fishing for, say, a poison roll to go with my weapon and I may be rolling something that won't roll poison ever.

Another question is, are fire builds worth chasing? I swear I can rarely get a simple combination of applying oil and then burning it while staying alive. Extra damage to poisoned/shocked/frozen/rooted is easy to build for, but fire eludes me. One time I got pretty far with firebrands, which melted enemies despite having some low paper DPS, I'm still not sure how that worked.

In the meantime I'll keep working on my parry and timing with slower weapons to see if I can ween myself off armadillopack, ice grenade, wolf trap, which seem to make their way into my items regardless of which color scrolls I'm using that run.