What can I do for cheap for dark hair turning prematurely white?

I have dark reddish brown hair and have been getting white ones since the age of nineteen. They are not gray but completely white and really contrast with my color, plus they are funky and sometimes stick out. I am now 27 and about 20 percent of my hair is white. I dyed it a year ago with a kit from the store, but it didn't stick to the white and just made the brown look unnatural and to dark. A friend said to pluck so I spent some time trying to do that (over three hours). Luckily I have a ton of hair. I'm not willing to spent seventy dollars every six weeks for a foil, and I don't want to be blond. Any ideas?