Most games sit at around 20-50gb each. 1tb=1024gb but after you put it in the system, it will leave you with about 800-860gb left. The stock ps4 has 430gb free before you do anything.
As this Gen goes on, game sizes are going to start getting bigger. Smaller Indie games that were at one point under a gig are now going to be considerably larger in size. For instance most games that are coming out Oct/Nov are at least to be 40Gb+. Also the updates for games are also growing in size. Lords of the Fallen is going to have a Day One update that's 5gb. And it was just announced that The Master Chief Collection will have a 20gb Day One Update. Do yourself the favor and get the bigger drive. Even if you have to wait until you can purchase it. Why spend $80 on 1tb, when you could double that for only $20.
Just my opinion though. I know on the PS3, I hated having to constantly pick which game I wanted to delete, just to install new ones, especially with PS+.