I'm going to be completely honest here, I've invested heavily in shellac and whilst I think it's good for decent nails, it's not great for thin/bendy nails unless over something like gel or acrylic.
I've spent so much on the system and have so many colours (which I obv keep replacing) that I'm kind of locked in! And i do like it, but it remains my least profitable service by a long way.
If I was choosing a system now, I'm not sure I would go with shellac as there are soooo many good ones now. But I might![emoji5]️
I have bought some gellux colours (plus base & top) which works fab for thin nails, I have about 12.
I wouldn't offer more ranges i don't think, I never mix products from different ranges and couldn't justify buying base, tops etc and maybe lamps as well from several different places, plus p&p would add up.