my advice is that take 3months at least before you think about appearing for GMAT. get some elementary maths books and revise the concepts first. only when you are comfortable with those, go for GMAT specific problems. Dont get into GMAT books right now. From what i could make out from your post math in general is a problem area for you, and practicing tough problems from the outset can make it even worse.
Yes you have scored a little low, but try & look at the brighter side. If you can score 600+ in your next attempt, and there is no reason why you can't, the schools would see you as someone who never gives up and is ready to fight it out when in trouble. So that's a good thing!
All the best!