I bought used games and new.
I bought new games if I want to support the devs so I do this mostly for Japanese games. I bought Uncharted all new aswell. I also buy new games if the CE is good. Watch Dogs 1.
I bought used games mostly for western games and some Japanese games normally from big publishers like Capcom or SE. I also buy it from other users as well. We don't have gamestop here and mostly Gaming stores here sell new games. It will be rare for you to see a used games from official seller here.
Although at the moment it's rare for me to buy a used games. Normally I wait for Flash sales and other sales on PSN.
So I was able to buy a lot of western games that way.
PSplus games also helps a lot.