what are some of the most op builds for this league?

Here's a list of some of the popular end-endgame(all bosses, 100% delirious maps, 1k delve+) viable builds in no particular order:

- coc ice nova assassin
- spellslinger vd necro
- vortex occultist
- cremation necro
- ed contagion trickster
- penance brand assassin
- fire conversion blade vortex assassin
- storm brand assassin
- spectre necro
- aura stacker ascendant/guardian (ek, spark, arc, penance brand, it doesn't really matter)
- stone or carrion golem elementalist
- iceshot/barrage deadeye
- toxic rain pathfinder
- ball lightning mines sabo

Things I personally wouldn't touch this league are totems, traps and pure melee skills. Everything else just scales better and gear really isn't an issue this league.

"

Some bow builds out there that are really insane strong, and they are not even stacking DEX. Not even a single cluster jewel. Just good old projectile count, frenzy charges, crit chance and crit multi.
https://poe.ninja/challenge/builds/char/Exasa/FarmingSimSpeedrunner?i=0&search=sort%3Ddps%26dps%3DIce-Shot

IceShot/Barrage is a very scalable build. If you put enough exalts (or mirrors) into it you can get those kinds of numbers. It's also a very high skill cap build. There's a difference between builds that are OP for anyone at any skill level on a casual budget, vs. OP for really good players on a really high budget.

"

when I try to build it myself based on a realistic budget for myself, I can barely touch 5M DPS.

This depends both on the build, and on your definition of "realistic budget". For example, a poison BV Assassin can be built to do 5m, 10M or 20M dps more cheaply than you can build an Ice Shot/Barrage Deadeye with the same numbers. The Assassin will also be a bit more survivable for the average player. But the Deadeye will have more room to scale dps on a super high budget if that's what you want. (At least all this was true last league. I haven't played either this league...)