Conquer!!! (just kidding)
most of the f2p's are pretty playable as a non-spender, just have to look out for the ones like conquer, you can check
http://www.mmorpg.com/gamelist.cfm for a way to check for just how "free" they are, but you're still going to have to check videos and the game's item mall(if it has one) to see if it fits your tastes/criteria since you were a little vague

Edit: keep in mind, some games have an item mall, but don't offer anything drastic, just cosmetic or minor "quality of life" improvements (like Path of Exile)
This post was edited by FriendlyCat on Oct 17 2014 04:22pm