Great question. Giving gifts can backfire faster than anything in the dating world. A basic human fear is having our options taken. If she takes the gift as a sign that you're wanting her to feel obligated, she'll start to feel trapped and begin pulling away.
The basic rule for gifts is "If you have to ask, it's too early." I've never seen a relationship harmed by being late giving gifts. (Unless it's an occasion where gift-giving is expected.) Even then, keep it within bounds.
The best gifts are shared experiences, like trips or activities. That way, you don't come off as needy.
You have to ask yourself "Do I want to give, or am I trying to buy her affection?"
You can ask yourself "Would I give one of my friends a gift under these circumstances." For example, I gave a girlfriend a briefcase when she graduated college. She saw that as a recognition of her achievement. If in doubt, go smaller.
I defy you to find a girl who says "I really didn't like him, but then he got me this great gift ...." You can't build a relationship by giving gifts. Once someone is in love with you, then you can gift all you want. In the early stages, it's better to avoid it.
