Well, I know only a little about stocks trading, as I'm interested mostly in crypto. The procedure of trading on a stock exchange and a crypto one is practically the same. The difference lies in what you trade.
On stocks, you could practice with small portions like it's usually done at crypto exchanges such as CEX (
https://cex.io/) or Bittrex.
There are many source besides crypto trading as we had the only traditional trading before the crypto world and we have still that tradition which is running on its way besides crypto world towards success. If you want to switch in to the traditional trading again then you can start from now but mind of a real trader says that trading with multiple sources is better than a single one.
Trading inside or outside crypto still all balls down to the general knowledge you have about trading and the strategy you have to be able to pull through and it all depends on how you are able to take advantage of those opportunities that comes lurking within those space.
For those who do not have the proper understanding, skills and experience, it would always end up being the same thing at the end of it all. It is a good thing however to at least diversify as long as you know what you are doing, either stock market or Forex or wherever you want to be diversifying into, just make sure you get yourself familiar with that environment first.