My name is Michael, I’m a Guru here with Shopify, thanks for getting in touch. :)
We have a handy app from our App Store that will allow you to set up promotions for members. It comes highly rated and there is a free trial with that app so you can try it out first before making a purchase to see if it's a good fit for your business needs. You can take a look at it here.
As for non-member promotion, what you could do there is set up a compare at price where you show what the price was and next to it will appear the current price. If you have the current price 10% off what the compare at price is your customers will see the promotion. Youo can see a guide on that here.
I hope this helps and best of luck with your Business going forward! :)