To be honest, I strongly disagree with the people who say they 'never' do three coats..... If your doing a perfect gel polish application, whether it's shellac, Gelish, OPI Gelcolour, or any gel polish for that matter, there is bound to be some colors which absolutely need three coats. If you don't do it to certain colors..... One: it's because it doesn't look like "it's needed", and that's because your definitely applying each coats way too thick....
Or, two, your doing two appropriate thickness coats, and letting your client leave your studio with a very see through, weak looking polish application. I can't let my clients leave unless the color looks spectacular in every angle of light.
Don't feel bad for doing three coats. Every single retailer even suggests some colors may need three coats.