dude i went through the same thing lol you don't need to build from scratch. can build on kalshi/polymarket apis, use protocol stuff like gnosis CTF, or full custom. depends on how much control you want resolution is the part everyone underestimates btw. oracles sound simple until your first edge case this basically answers everything you're asking: https://interexy.com/how-to-create-a-prediction-market-platform saved me a ton of time when i was figuring this out