what's the most popular extensions? I'm booked onto a shellac polish course but want to organise my next training while I have the money. There is a complete course which covers fibreglass, acrylic, gel and silk but I wondered if I need all 4, aren't some a bit outdated and obsolete? Alternatively there are single courses for both gel and acrylic and I'm a bit confused of which route to take. Any advise would be greatly appreciated. Thanks xx