Coinbase is stable and one of the original crypto exchanges. In addition to a nice layout that is easy to use and read and a wide assortment of crypto currencies to buy, sell and trade, Coinbase also offers leaning Rewards which are very short videos about various crypto coins and a few easy questions about each one.... when you're done, you will receive $25 worth (or more) of those coins in your Profile immediately --- you can hold them, trade them, sell them or withdraw them. When my wife joined, we both got $10 in Bitcoin once she completed the little quizes and then added another $75 into her account.
I'm very impressed with Coinbase and it's other service, Coinbase Pro, which you automatically get to use once you're signed up on Coinbase.
It's time to get your Invitation.codes account too 😎