Just a disclaimer.....everyone's hair is different, so this is just my personal experience. Take what you want from it
I know how you feel!!! I was in the same boat as you or a long while there...I just got tired of spending so much money on my hair, but I just couldn't STOP. Recently, when I lost my job and got pregnant, I resorted to just dyeing my hair one colour. I thought it would look aweful, but I use the feria hair dyes, wich give it such a dynamic shine. I've had some pretty aweful hair experiences in the past and once had to chop it all off due to a bad bad incident involving a perm being left on for too long...so I am pretty picky about what goes on my hair. I am pretty pleased with the L'oreal line of hair colours...Feria is great if you want to stick to one colour....but the clour has a dynamic look to it.
If you still want to stick with your highlights, you have a few options.
You can go with a cap. I had problems with this, because my hair is wavy and longish, and the cap was so hard to use. Plus, it doesn't look as nice after a few dye jobs because you are picking out different strands each time....and after a while your hair just looks all blond and not highlighted.
Foils work nice with these products because you can single out strands from each other...but they are hard to do without help and some sort of experience doing it.
Brush on kits are pretty nice, and they allow you to target roots, or even do more then that. I found these kits nice to use, and it gave me control over where I wanted my highlights....wether I wanted them chunky and thick, or nice and distributed.
L'oreal has a kit called "hi light styliste" which isn't that hard to do on your own, and you can control the colour you want and how long you keep it on.
If you want golden highlights, you can buy a haircolouring kit and use it as a highlight kit...just get a brush or your own cap, and you are good to go. When I did this, you can mix a little bit of the colour together and "test" it on a piece of your hair.....you can see how the colour looks and wether you like it or not.
Once you do this once or twice, you will become a pro at it, and soon you won't want to go back to the salon
I love playing around with my hair colour now that I know which products I like.
Sorry this is so long...