What are the best MMO games on Steam based on my own preferences?

For a long time I've only really ever played single-player games, or games like Borderlands where I can have just a few of my friends play with me. There have been very few MMO's that I've actually played up until recently. I'm not big on a lot of games like Elder Scrolls: Online or anything like that, but I did like Skyrim. The online version just doesn't seem to interest me that much, and I don't really want to waste money on it. I have a high-end gaming laptop that can run games like Ark on highest graphics will still over 70 FPS, so I'm not too worried about how beefy of a computer I need to play games; when answering don't leave out a game just because you think it might need good specs. Any suggestions are welcome. However, be sure to suggest mainly Steam games, unless there are some good free MMO's on the browser or other sites. I prefer games with a lot of character customization options.

The games that I play that are MMO/Multiplayer that I seriously enjoy are these:

-Transformice (Not normally my type of game but at this point I've spent nearly $300 on it)

-The Isle (Survival-based dinosaur game)

-Wizard 101 (Again, not my kind of game, but a friend got me into it a few weeks ago so I play it some with her, and it's decent)

-School of Dragons (How to train your dragon online game)

-Cereal Soup (Multiplayer game where you customize an animal character and run around, a lot like Feral Heart. Nothing like Animal Jam though.)

-Garry's Mod (Rarely play multiplayer though