How to get hair blonder and QUICKER?!?x?

Got my hair highlighted with a full head of blonde highlights about 2 weeks. They are starting to grow out already, but the blonde came out best in the top and just parts in the bottoms because iv had my hair died so many colours and so many times. Going to be getting my hair died again in about 2 weeks again. Does anyone have any tips on how i could make sure theyll come up better next time or how to get my hair blonder and quicker. xxx