Home dye over salon colour

[Bumbleby]

Hi
My natural colour is dark brwon, now with a good many greys. It is also very thick.
Recently to disguise the increasing greys, the salon has been dyeing it dark brown to match my natural colour and I have been having highlights to break it up due to the volume of thickness
As it grows, there is quite a contrast between my natural colour and the highlight, plus the addition of greys
It costs a fortune to have this done at the salon, especially now I need it done more frequently to hide greys. I am not completely grey yet, but want to hide the greys, at least until I am completely grey ( or as longs as possible). I want to find a more economical way of managing this.
If my hair is just dyed one colour to match my natural colour, it will be very dark. If I get it dyed one colour but a bit lighter, I will have to manage my routes due to the contrast, which will mean frequent salon trips.

I still have highlights, would it go wrong if I dye my hair all over with a home dye kit in a medium to light brown? Knowing my skills it will be a disaster, so any recommendations would be appreciated thanks

Sorry for the typos

I would start off with a semi permanent-Nice and Easy is the best. I use light ash brown. However, it won’t lift your hair like a permanent colour will so you can’t go lighter. But if you match your own colour with it, it will be more translucent and not so heavy-it also doesn’t build up on the ends as much. It covers greys pretty well. But until you grow your permanent colour out, it will fade and it will be noticeable. I’d be reluctant to lighten dark brown hair with a box dye-it might go brassy. Could you ask your hairdresser for advice-that you have to economise so what’s the best thing to do?

I have highlights through the end of my hair but not at the roots - more like a balayage. I then keep up with the roots in between (MIL used to be a hairdresser which helps and she puts a box of L’Oréal natural brown on the roots). I then put a toner through the ends to brighten up the highlighted bits in between salon visits.