How do I fix my hair colour?

[mrs. joejonasbby!<3]

ok so my hair is naturally almost black but not quite yet, its like a very very veryy dark brown. The bottom half however, is brown, kind of like a dark brown that looks auburn in the sun. how do i fix my hair color to be just one? and i want it to be like a dark brown all around that can kind of mix into the color of my natural hair because i dnt want to keep dying it over and over again, but keep in mind i dnt want it to be any darker than an expresso color, expresso itself is to dark. i also want to do it at home since im currently unemployed and i hardly trust anyone with my hair and my hairdresser is expensive. haha any help or suggestions?