Check with your local warehouse as some will do starter packs for specific brands. When I started out, I used Osmo ikon and Matrix.
However, be wary of choosing products based solely on cost as;
a) you need to be familiar with how the product works so look out for free colour courses if possible, and
b) a successful business is one that has plenty of repeat clients. If you use poor quality colour, it might not cover grey as well or fade too quickly etc. and your client won’t be back.
Also, you don’t actually need to stock many colours.
Generally, when I do a cut I use the opportunity to do a colour consultation with a patch test. In every case, I’ll do a patch test beforehand and that gives me enough time to buy any colour tubes, fresh developer etc. that I might need.
If you’re mobile, it pays to be super organised.
You don’t want to be lugging the equivalent of a full salon of products with you every day so if you store things in clear boxes, it’s easy to see what you want and grab only what you need before setting out.
Co-location is my mantra.
So, styling products are together in one box, permanent tint tubes in another, developers in another, rollers and perm equipment in another box etc.
I have a basic checklist I use before setting out and I recommend that you keep a detailed inventory and update it regularly.
Best of luck!