T.C.
I have been a hairstylist fir about 10 years so hopefully I can help you out a bit. Do you have a sallys beauty or something similar where you live? They sell better quality hair color then the box stuff. The girls that work there are pretty helpful and you dont need a license to buy there products.
I would get a semi or demi hair color not permenent until you know you like it. The color goes in levels 10 being the lightest and 1 being black. If you want medium brown I would start with a 5 or 6. Look for a 5N. If you want a reddish brown you will want to mix a 5n with a 5r. I would do 3/4 of the 5n to 1/4 of 5r. You buy the developer separate and mix them equal parts. The insructions are on the package. you can use a bowl and brush or a bottle to apply it. Make sure you do small sections at a time so you dont miss any. Leave on per the time on package usually about 30 min. Just apply root to end. I will cover the blond just fine.
hope this helps you. Let me know if you have.any questions.