I need the best hair dye!?

Okay I have been dying my hair blonde for 13 years, my original color is medium brown and I want my color back, I don't care if it is exactly the same. I have dyed my hair several times and it fades back to blonde in less than a month. I tried a salon product and got the same result. I'm tired of the roots and I want brown hair and I want it to stay! Please help! I do NOT want it done in a salon. Thanks for all with help & please no kiddie answers.