My best advice for coloring your hair at home is don't do it!!
Box dyes are progressive and metallic dyes. Meaning, it might look great the first time, but eventually you'll end up with lighter roots and darker ends.
Using at home color (box dyes) will pretty much ruin your shot at getting a cute summer balayage without paying a corrective color price ($$$) and damaging your hair.
Box dyes are designed to get my best friend (dark brown, curly hair) and myself (light brown, straight hair) all to the same beautiful shade of blonde shown on the front of the box. Sounds impossible? Don't try it! When you go to a professional, they use different levels of peroxide based on your hair type and formulate special colors to get to your target shade. The box does not know what kind of hair you have, so it is the strongest level of peroxide. The result is a lot of damage/dry ends, or, for girls with more pigment in their hair, incomplete results.
A bad at home job can cost a fortune to fix. If you find the right stylist, you will get better results, always. Most of my now super loyal clients were doing at home color because they weren't sure what they wanted and it was often impulsive. My advice, see a trusted stylist!