I brought shellac which clients love but when they had all the bright colours they wanted more, done additives & glitter & art but once they had that they still wanted more brighter colours in summer, all my clients are under age 30 at minute, so I brought Gelish & all I have used in past month + is Glow collection, with glitter, stripes, marble, art etc and in one week I got 5 new customers all they wanted was glow colours that I put on my fb business page, there s nothing wrong in stocking both if it brings in new customers and it certainly has for me.
as long as you explain that they both are different polishes but my customers just pick what colour they like and are all returning.
So maybe start by buying Glow collection & see how you get on.
Just to say I love shellac
Hope that helps. X