If she likes flowers, you can't go wrong with them. Try and slip in a subtle conversation about what flowers she likes. That way you can't go wrong.
Give her a "Spin Spa" its right around 20 bucks. Not only will she love it but she'll think about you every time shes in the shower.
Flowers, Gets you a Girl's heart (And write her some kind of a SWEET message) or reserve her a place in some spa (If it is 20-50)
dont think normal buddy, just be creative , why don't you give a pic in which you and your gf where taken a slap. other wise give her a family photo of her family, just for surprise.
What about a small photo frames with key chains. You can have your or her photos in it. It cost about usd20.
Have her name tattooed on your had WARNING: I'm NOT responsible if she dumps you or you dump her and the tattoo never comes off! lol
Never hesitate giving the most expensive gift's to your girlfriend! If she loves you and you love her , you will make her really happy. Try to order a suite, some roses, romantic songs, jacuzzi and champagne! I don't believe you will spend more than $500 for all of it , its just $500 though but don't forget something, you can have $500 today and $10 the day after tomorrow , what really counts in this world are memories , happy memories of you and your lover