There's newbieness in different forms, crypto newbieness and trading newbieness.
If you don't have a grounding in how fucking gross crypto can be then your trading will be even more disastrous than it was going to be anyway.
Think of all the things you need to be aware of - plagarised white paper piece of shit projects, fake volume exchanges, exchanges springing KYC on you, exchanges flat out stealing from you, malware wallets. The list is a very long one. If you're not immersed in some of the basics then you may well head straight into disaster.
I don't argue what you are saying, in fact, I agree to all.
Still though "my" question remains unanswered, for both newbieness forms that you mention (crypto-trading).
When does a newcomer know the right time to get on a wagon and start trading? Which wagon he will choose is another thing. Besides almost all exchangers have the major coins and are more than enough to take a pick.