Very few and most will need updates so even with a small install you need space for the updates, the need for speed games have small installs but if you buy need for speed most wanted and think that it only needs the 250mb for the install you'd be wrong, it also needs 2,7 GB for updates so actually takes 2,9GB in total plus a few MB for saves
just buy yourself a hard drive and bracket when you can and don't buy anymore games until then, and of course hope gta5 doesn't need any more space for updates if you want to play online.
a 500GB hard drive is only going to cost you $50 and $5 for the bracket, a 1TB hdd would only be about $20 more by the way and is worth the extra cost since even 500GB will fill up fast once you start buying a lot of games and if you get psn +
I spent a total of $87 including taxes to upgrade a 12gB ps3 to 1TB for a friends birthday gift in may, it was cheap, easy and worth every cent