hairstylist - help!!!!

I know this is a period app but I also know there's a good amount of stylists on here so why not ask! So I had platinum blonde balayage. Over time it became brassy and warm of course. I didn't want to go spend $150 to get it done again so I bought my own stuff and tried it out. I did really well with the fading and all but I totally messed up on the toner. Some of my hair is still brassy while the ends came out purple/grey. It looks weird! I want to get that platinum blonde back and I know my stylist would get it right on the first try but I just can't afford that right now. Any advice to get the purple out and get a brighter blonde all around? And how soon can I fix it without hurting my hair too much?