This is newbie talk, so don't kill me. I want to learn, but it seems so complicated.
I want to - sell BTC for ETH, and then sell that ETH for more BTC than I started the trade with. Sounds like a simple way to start, yet I know it won't be.
My biggest concern is that there are so many exchanges. How the heck do I know which ones will pay me after I make an exchange? I know I have to check their reserve balance, but what else should I look for?
No exchange is going to pay you are create coins for you they are simply a marketplace where people list their cryptocurrencies and find the buyers basically something like eBay.
There are lot of exchanges are here, for beginners Binance maybe good so all you need to do is just register there and deposit funds or cryptocurrency to start trading.