I use BitMex for trading BTC with leverage. I use Binance and Shapeshift for trading altcoins.

I would take some time to read some basics about trading and risk management. Babypips is a great resource for new traders. I can't emphasize enough that you need to constantly be thinking about risk. You want minimal risk, maximum gains. That means carefully planning where you want to enter and exit a trade and most importantly, where your stop losses are. I recommend checking out Tim West on Tradingview and CarpeNoctom on Twitter/Youtube for trading strategies and ideas.