DON'T DYE YOUR HAIR BLONDE! It will be an absolute disaster!
When you dye your hair red, you put a lot of red pigment in your hair, which is very hard to strip out, but if you try to put a blonde colour on top of that, you will end up with very streaky, orange hair. It won't work.
Unfortunately, you need to go through the process of stripping your hair of the colour it is currently dyed. I'd suggest buying a heavy-duty dandruff shampoo (such as Head and Shoulders or Vosene) and use it every day for a week at least - leave it on overnight, even, if you can. This will strip quite a bit of the red out, I think. After that, I'd suggest forking out and seeing a hairdresser. They will be able to give you professional advice, and will be able to begin to strip you hair with bleach. They will be able to gradually bring your hair colour up to blonde, without turning it orange, and will be able to tone any brassy sections down.
You'll need to see the hairdresser a few times, and it will cost a bit, but unfortunately that's the price you pay for going red!
If you don't want to do this, and don't want to spend the money, it's going to take a long time for you to go from red to blonde. You will need to continue to strip your hair of it's colour until it is 99% gone, and then do the bleaching yourself. My advice is to see the hairdresser, because SO much can go wrong when you try to lighten your hair yourself! Either way will damage your hair, because bleaching always does, but the hairdresser will be able to advise you as to how to prevent as much damage as you can.
As a final note, I'd suggest that every time you have your hair bleached, you should HEAVILY condition your hair. Leave it in overnight, and for as long as possible.
I've had to strip my hair from red to blonde before, and have done it myself and with a hairdresser - the hairdresser is the better choice!