Isn't that up to the traders themselves personally? Like at most I'd say to diversify, but how much or how little highly depends on what the trader thinks of the assets they're currently trading with. For investments it varies really, getting the top ones usually isn't wrong but if you want to profit more, gotta take a lot more risks as well as a bunch of research to possibly minimize that risk. Other than that I'd say it's closer to just trial and error imo. Trading WILL lose you money, that's for sure. Just a matter of how much before you can learn what works and what doesn't.