As long as you have a well rounded collection, 15 colours is more than enough.
There will always be more colours to buy, and you can add glitters on top of the ones you already have to make them a bit different.
The hardest thing to do is pull the clients in. I work from my home-based salon so constantly have to fight against having no shop front to get noticed. I find that leaflet dropping works really quite well - I haven't seen any other salon leaflets come through the door since I've been here either, so its kinda an untapped market.
When you are designing your leaflets, I would advice you to make them VERY clear and easy to read - don't try to shove too much on there, have a link to your website and Facebook page to find out more. Also include at least a few really good quality - perfectly executed polish, well-lit and tack-sharp - pictures. It really draws the eye and elevates your brand from any others they might have seen.
Don't be afraid to sell yourself. I'm talking about really stating how awesome you are at what you do. Post pictures of your work regularly, change up content on your website/facebook page so that its fresh. Interact with your customers - don't just sell to them.
use any local Facebook groups. For example, we have a few groups for my town. And one of them has just allowed local businesses to advertise coming up to Christmas. Cue me writing an pitch and adding some pictures.
and finally, when you do order your leaflets', don't leave it up to your boyfriend. Do you have any idea how long it going to take to deliver 10k flyers?!