I'd advice myself to not get involved into trading to begin with. Retail trading is just waste of time and money.
The second thing I'd advice myself would be to... Keep learning more about the crypto space. Maybe don't create a dozen of topics asking basic questions which could be answered with a google search, but yeah, with everything considered, there isn't one thing I regret about learning.
(Ok, maybe I convinced myself to buy a little more

)
I'd advice myself to not isolate myself from likeminded people particularly those in the crypto space. Yes, I know we can learn alot of things about this crypto from YouTube and other places on the internet but me thinks we learn faster when we have friends and colleagues teach it to us and are always there to answer our questions and resolve our confusions. We may have to work twice as hard to get the answers if we were using the internet but a candid conversation with friends may resolve our issues within minutes. It may not be deep but it sets the foundation for other knowledge.