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?
If you do have plans on dealing or making fiat conversion then stick with CEX.
https://coinmarketcap.com/rankings/exchanges/Binance is on the top which i could assure you since its one of the most famous.
If you dont like to touch up centralized platforms then you could opt in DEX.
https://coinmarketcap.com/rankings/exchanges/dex/So its your choice to make!