I know...it can be expensive. You can get a box at the drug store for a lot less!
You or a friend can apply it and it will be fine, right?
Well, not really...do you fully understand the color wheel?
Do you know what underlying pigments you are working with?
How many levels of change do you want to see?
Do you have old color in your hair, you know you may need to deal with that differently.
IF you find a color that works, I recommend staying with that color, as there is a lot more to consider when changing color.
If you have a hairstylist, and want a color that suits your skin tone etc....use your stylist and all of his/her knowledge and abilities to have a color you will love.
If you are looking for a great stylist, look at groupon. Once you find a stylist that you love, stick with them!