It doesn't matter if they all get lost (they will) the impact of a $50 books is bigger than a $1500 training course, and doesn't require any lost billing-days. So what should you buy?
Get a one good book each on:
I suppose you could thrown in something on data modelling as well - but seriously if you have the head for data modelling you're fine, and if you don't a book isn't going to help. Same for UI design. For the record I have a head for data modelling, but I always need help with User Interfaces (Thomas! Mahesh!).
And this post is not proof-read because I don't have time. I'm going to try and post more often now, which means less quality too.
Amazon List Here