- Coinbase is probably one of the most established platforms, so I would trust it. Plus it has great design / UX and good mobile apps. It currently offers bitcoin, ethereum, and litecoin, but I presume they'll add more currencies over time. They also have a section on their site to Learn about these products and a blog you can subscribe to, so if you're new to the space, then start here!
Coinbase is there to get you started; it's easy to use and understand what you're doing. The transactions feel safe enough, and it protects you from buying too much at once. It genuinely seems like they take care of their users, especially new ones.
I have been waiting for a week now for my funds to become available on coinbase and they still are not. Plus, I have had zero feedback from the support team for a week now. Do not put your money here. Seriously.