So, which is the best source of crypto trading signals, and which one should you use to make money?
None. Sorry and please remember that. Go Telegram and you will puke in the number of people that will suddenly PM you out of nowhere. I don't know how they do it but targets are mostly like you who are looking for help in groups. Those are all scams or if not they want you to pump one dead token for they will have a chance to sell it at a better price.
Just read the market, that's the basic thing that you could do. Don't believe on people or groups that uses crystal balls to predict the market.
You could be right with that because in the end what they are providing are just signals and nothing more and sometimes a signal can fail too so there is no assurance that the money that you paid for a premium subscription are going to be worth it.
What you said about telegram is so accurate as it happens to me all the time but that is when I am new to this app but not anymore until I found out that you can make your self safe from those scammers by just going on to your account setting and off that one feature there. A short google search can show how to do this. Reading the market might not be enough but searching for some information about the coin, like watching news could be helpful.