Hi
I just had a quick peek at your profile. Doesnt your training provider give you any materials, or at least recommend a brand and tell you where to purchase it? If not, you might want to consider getting out while you can and finding other training, because a big part of your training is knowing your product. Different products work on different mix ratio's and with different application techniques, and if they are giving you generic training, it may not be compatible with the brand you select, and you would have no guidance as to whether the brand you select is any good, or even if it's safe to use! (do a search on here about products containing MMA).
Personally I wouldnt buy any professional products from Sallys. As far as I can recall they sell Star Nails, which isnt a particularly good brand. If you do continue your training with this educator, you might be as well ringing them and asking for details of what brand to use and where to get it.
good luck and I hope you enjoy your training.