I've never died my hair before

i've recently gotten a few greys

and also a hair dresser died it a lighter color half a year ago without my permission and now part is my original dark color and part is a litter color

how do i choose a color whether like my dark or the lighter, how do i choose a good color

how do i know which makes are better easier to use

are their some without chemicals that are good
are the exorbitant in price

what helps with the process of dying like someone one told me put vaseline around the edges of your head to stop it spreading

are their other hints pleas eof how you do it.

thanks.