
It's not about all that...
Valentine's Day isn't about money:
http://www.14february.info/?page_id=109. The main thing to remember is that Valentine's Day isn't about spending money - it's about spending time and effort, and showing you care. You can be broke and still make an awesome impression by putting some thought into it.
If you're not rich, your guy/girl likely already knows you're not rich and they're not going to expect a hugely expensive present - in fact, if they love you, they'll more likely be cross if you blow your cash on something that'll die within a day or two. Just put the thought in, that's what matters.