You might consider doing something that will really put a smile on his or her face. I like candle light dinner, so maybe you can also try that
Yes, this is also what I'm thinking.
No need to spend that much.
Invite her to your house and cook the food by yourself and for sure that she will appreciate it. I wouldn't dive much what will happen next but that would be a romantic dinner that the present girls would want to have when most are into materials.
it is not about the gift as much it is about the effort you put in it to make her happy, find what would make her happy the most and do it.