I only play limited (draft and sealed deck) game formats, where everyone is by definition on equal footing. There are entry fees to these games and prizes for doing well, so if you do well enough, you don't need to pay anything. Also, Arena has a system for constantly giving you some gold if you play often enough, which also helps. In my case, I've put in $100 into my account last August, have easily played couple hundred of hours since then and still have around $40 left. I'm a decent player though.