I almost feel like this doesn't need to be stated, because it's so bloody obvious but I guess some people must be falling for it.
Let's think it through logically...
If you have a guaranteed way to turn one dollar into a thousand, you have a guaranteed way to turn a thousand into a million and a million into a billion. Are these people Warren Buffett or George fucking Soros? No? Then they're full of shit.
If you had a trading strategy that was yielding massive profits, would you give it up for a few Steemit votes or a subscription fee? Would you teach courses so that 1000 other people do what you do, making it more difficult for you to keep using that strategy? No? You'd probably just keep trading right? I mean, you'll earn far more that way.
The best you can hope for with these people is they're using their notoriety to pump something and they might let you come along for the ride some ways, but you have no guarantee they won't dump with you left holding the bag.
This is different from trading news or someone saying such and such coin is looking cheap at the moment, that's fine but if someone's offering to teach you trading secrets for a low monthly fee, run a thousand miles in the opposite direction. Especially if it's "guaranteed".