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.