i think you should DO something memorable, though a gift would be nice. If you wine and dine her shes going to remember that more then a gift.
for $200 this is what i would do (dont tell her your plans for the night)
1-Buy her 24 red and white (12 of each) roses
2-Pick her up about 30min before the sun sets and drive somewhere with a good view like beach, cliff etc etc
3-Watch the sun go down with her and as it goes down give her a nice kiss and tell her how much you care for her (maybe even love her) then give her the roses and say something sweet (i would give you a line but i fly by the seat of my pants in these situtations, sorry mate. Im sure your up to it though)
4-Now you could either just take her for a spin at the beach or head of to a nice place to eat. The idea is you end up at a nice place to eat.
5-So now your at the place (maybe even find out her fav place and go there), just have a relaxing evening with her and give her some small but thoughtful gift... just have a good time with her
6-After dinner head to a nice late night cafe for something sweet and try something euro style
7-After desert just take the long way home, maybe if she seems up to it stop somewhere with the top up for a little
8-Then drop her off at her house around 1am (or whatever time she has to be home) give her a nice kiss and send her on her way
Ok thats enough romance from Rob for the day. I think a girl should be whine and dinned, forget the gift just show her a good time. If its a good relationship (aka in it for the right reasons) she will most likely enjoy this more then an expensive gift. Something to remember its the small things that matter if its really special for both of you go out of your way by holding the door for her or pulling out her seat (not to far she might fall hehe, no one ask!). Whatever you do unless you normally order for her DONT, from what I can tell girls dont like it.
Possible small gifts:
-framed picture of you and her together, something memorable
-understated necklace with some pendant ex heart, animal etc etc
-earings (something simple but elegant, make sure its @ least 14k gold though)
On the topic of waiting till marriage, its up to you. But theres nothing like sharing that with the woman your going to spend the rest of your life with. To be frank you never know how long this relationship will last not to mention, there is some stress in having sex; you could knock her up
and thats no fun. On a personal note, it seemed like a good thing to sleep with my last gf but now i wish i hate waited.