Just read the PHB. BG3 follows the 5e rules exactly, with no deviation whatsoever. Anyone who tells you otherwise is a liar. Don't listen to them. :P

Kidding, but seriously, you should head to the Larian Discord and play with some folks over there. Fastest way to learn and you can get answers to questions in real time.

This site is having some issues right now with lag.


Here is the Larian Discord
https://discord.gg/cUJX6e5B

Also Wolfheart has a discorbs that is really active with a lot of knowledgeable peoples.
https://discord.gg/rK5P7Xnd

Good Luck.

Blackheifer