I use opi in my salon in spain, and i love the products, i find some thing expensive but they are defo worth it.
The only thing i would say is don't get roped into using their cuticle pusher and nippers, i'm sure they're great but they cost a fortune and are not really any different from a basic pair. Opi used to go on at me to buy them and i just refused, they've given up now!
You could even get on OPI online and order. I use it but cant remember how much the whole salon kit is. When I started, I started with basic stuff, purchased on at a time and then moved up from there. Clients arent going to know you are missing a type of hand serum vs. an exfoliating scrub. Plus, you could buy the whole kit and maybe never use everything in it. Well, good luck anywho!