have been highlighting my ash brown hair at salon and can't afford any more. What color can I use for an all over beige/blonde shade?

depends on how light or how dark you want it.
you gotta be careful with home products as they can go a strange colour if not done properly.
stay away from ah colours as they can go a blue/green colour.
but go to a salon and ask for their advice!
they would be happy to help and that will prevent a disaster from happening!

Highlighting ash brown is usually done with bleach. There are highlighting kits that you can use for that -- or you can go to beauty supply houses (Sallys, for example) and purchase the items separately (cap or foil, bleach, developer).