Been playing Warframe for the past couple months. If you like Destiny 2 then you'll prolly like it.
It's free to play, but I like how everything in the game can be attained without spending a dime. There are cosmetics that are locked behind the premium currency (platinum), but you can sell in game items to other players for platinum to buy them. I spent ~$60 so far, but don't think I'll ever need to buy more when I can just sell items. I figure that's about the price of a premium game anyway, so I'll get a bit of a head start as well.
It's honestly a great system, and I hope more free to play games follow this model in the future. There is a lot of grinding, but that's kind of expected from a game like this.