The ones you have listed here is enough and they are okay cause they are legit. And just like you have said, centralized exchanges are easy for newbies to make use of… most noobs wouldn’t understand how decentralized exchanges works. When I started making use of cryptocurrency, I started with Coinbase… everything about them is easy and they are legit, their site is well secured, although I’m not 100% sire about that. But from what I see while making use of their site, I believe it is very secured.