There are many types of algorithmic trading. Certain platforms host regular competitions that will allow you to submit trading algorithms that meet certain requirements, best thing about that is, if your algorithm performs well enough compared to the other submissions, you will be rewarded with cash or other prizes. Some platforms also offer the ability to get recognized by institutional investors and which comes with the potential for institutional licensing of your algorithms.
I personally liked Quantopian but it is not available now. QuantConnect, Quanticas, and MetaTrader are good. Quanticas is best for the competitions. Meta Trader is good for the basic forex system. But if we consider various factors, overall I would suggest quantConnect.