You can, BUT you have to check with your insurance provider. Alot of insurers wont cover you unless you have done the specific Gelish course. Even the generic "UV Gel polish" courses dont cover you for the insurance.
Even saying though, I thoroughly recommend doing the proper course. I didnt do the course when I started out (but had it booked) and I had no confidence. As soon as I didthe course I learnt absolutely LOADS! And so much more than I ever imagined I'd be taught on hte course. Its not just about applying Gelish, its all the other bits that go with it such as repairing broken nails, removal, product chemistry, usin structure gel correctly, having someone watching over you so you know its being done exactly as intended and having someone to go back to if you have any problems.
Using Gelish is not as simple as just applying it like a normal polish.
Now I never doubt myself with my Gelish as I know Im doing it all correctly, I dont get scared when my phone rings and have so much more confidence in myself.
xx