My hair is a nightmare please help...root problem and dye?

Hi guys,

I dyed my hair with loreals brasilla dark brown about a few months ago but it was black and i hated it so i went over it with nice and easys natural brown which toned it down a little. I decided i wanted to grow my hair out and have my natural colour which is auburny brown but i have grey hair (which i didnt now about coz i have dyed my hair for years...im now 25). So now I want to dye my hair like a cool red or purpley brown colour but i have about half an inch of root which will take to the dye brighter than the rest of the dark dark brown i have on the rest of my hair. Any suggestions??? I was thinking doing a pre lightener first. If I do what colour should i put on top of a pre lightener?? Would a bright red look silly with the orange tones of pre lightener?? Or should I stick to an ash brown?? I cant aford a salon either!!