You don't need to be rich to give very memorable presents for your girlfriend.

You could be more creative and use your imagination to find unusual present.
Just imagine the picture - you are going through the park and find a field with clover.
All you need is just to find a four-leaf clover and present it together with small note.
You can write something like - "This is your lucky clover and it will help you." or "I got lucky when I found you and you are the best."

She will like the present.