$500 is enough. In fact, I could say that it is a fair amount. You can double it but it would depend on the coin you are going to use, preferably, you want to use those coins that have high volatility. Regarding the platform, there's a lot of good exchanges but Binance is the one I recommend. I would say it is worth it but it really requires a passion and knowledge in dealing with this kind of trade 'cause you must always be active and watchful to market chart. If you have no much idea yet I don't recommend this one, probably long-term trade would perfectly fit.