I finally figured out how to do it, and I'll write you guys a nice step by step guide.
First on your PS3 Main Menu you have to go all the way to the left and create a new user. Next, sign into your PS3 and your new user. Then go to PSN and create an account for it. Email just needs to be in the
x@x.com format, because they don't send an activation email. Make birthday the current day and the year w/e you think will give the best car. Put in your address it makes it easier, because Sony actually validates the inserted address. For username and password it doesn't matter, but to make it easier remember to check the save password box. Once it's created, go all the way to the right on the PS3 Menu and press add a friend. Add your main account. Go back and switch users to your main account and add your new account. Switch back to your new account, open up GT5 and go through all the first time screens and then you get a gift card for a car.
Don't use it! Go buy a used car first. Then go to Items and find your gift card and press triangle and gift to friend and select your main account. Once the gift is sent, quit Gran Turismo. Go into the game tab of the PS3 Main Menu and open the Save Data PS3 and delete the gt5 save. Then open up and again go through all the first time screens, then buy the used car and gift again. Keep repeating as many times as you want in the day. After you've done this enough, go to your PS3 main menu and switch to your main user. (Do not delete the new user! You will have wasted your time!) Once you've switched to your main user open up GT5 and press GT Mode and the Community Tab will have a Star. Open it, go to gifts, press receive all, and you're done.
The cars you get will also depend on your A-Spec level, so I recommend you save those gifts until you reach level 20, so you can get the full potential out of them.
