I don't buy games I don't plan to play, except...
Bundlemania and Steam Cards cahnged all that over the last 12-18 months for me. I would buy a bundle for one game i wanted and then activate the rest and idle them to get cards. With proceeds from card sales I managed to get some games I wanted but would never have paid for. Then I discovered Steamgifts, and I could gift the games to gain levels on SG and qualify for better giveaways. And I won some good games!
BUT! That created an entire time sink for me: scrolling through Steamgifts constantly, checking every bundle all the time, spending time creating giveaways, leaving my computer on over night just to idle games, etc. And on top of all that, my monthly spending on games was growing! Sure, I was getting more for my money, but I was also spending more money! I fell into the consumerist trap. Think how much I'll save by buying this! You always save more by not buying it.
However, I have successfully backed away from all that and am in a much happier place now. I have many many games I do want to play. I am playing several of them now. I waste less time and money on shopping for games and related activities.
I still have wishlists, but the pressure is off. I can more realistically say to myself: I will probably not have time to play that game until next year. So I can afford to wait.