Difference between salon toner and home dyes/drugstore hair colourants?

I forgot to mention that I always use purple shampoo and conditioner, but it still goes a bit patchy in places- so someof it is quite light blonde, and some is brassy blonde with warm/orangey undertones 🙁

Here is a pic of my hair- you can't really tell but its quite orangey in natural light, but you can see how I have roots and darker parts underneath.

Permanent 'box' dyes in blonde shades usually lighten hair and tone/ add a tint, but in order to be able to do this and work well on a number of different hair types they usually contain a pretty strong developer, which could cause damage with repeated use. I am assuming that the toner your hairdresser uses is the type that is mixed with developer,but it will probably be mixed with a low volume one as it is deposit only (not lightening your hair, just depositing the tint). Most people on this forum don't use these types of toner as they don't tend to last any longer that direct dyes (which you don't mix with developer) and are more damaging in the long run.
There are some wash-in-wash-out colours you could try as a toner, or you can mix a couple of drops of a direct dye into a white conditioner and make your own toner (Adore browns can be diluted to enhance deeper blondes, certain purples can be diluted to reduce yellow tones etc). These can be applied as frequently as you wish as they don't cause damage!