How do I dye my hair?

My hair is naturally medium brown, and has been dyed a few shades lighter twice, and I then added warm dark blonde highlights. I REALLY want to dye my hair purple black with blonde dip dye. How do I achieve this in the cheapest way (at home because it’s so much cheaper)?

Hahaha I’m not going to the salon, people don’t realise how poor some people are when they have to go to a greedy boarding school :S well anyways it’s either home dye or not at all.