How to get started

I am 20 living in Los Angeles. I have a CA LLC set up, but that’s about it. No Amazon Seller’s Account (just a personal one), no seller’s permit, no reseller license, no business license, no sales tax exempt, no brand registry, no trademarks, etc. How do I know what to do? I want to do EVERYTHING correctly so I wouldn’t mess up in the future in terms of legality and taxes. Thanks.