What is the best way to Die your hair without going to a salon like buying a kit from Walmart?

I have Blonde Straightish hair and I have never died it before my sister says it usually works better to use 2 different colorsWhat is the best way to Die your hair without going to a salon like buying a kit from Walmart?
If you want to mix two colors, you should go to a beauty supply. You would just buy the two colors you want to mix, and the developer. It's important to know which colors will work together.