Eunice here from Shopify, welcome to the community, and congratulations on your new business!
While there's no denying jewelry is a saturated market, there's still plenty of room for newcomers! I recommend checking out the ultimate guide on how to start a jewelry business by Shopify, you'll find it here. It's specifically written for those who make their own jewelry, but if you're buying jewelry stock from a supplier it's still a fabulous resource to keep on hand.
Also, if you haven't already, I recommend working on your brand before you open your store. This means deciding on a business name, logo, and colors. Check out this awesome branding guide by Shopify. It walks you through why branding is important in a crowded market and the steps you need to take to build your brand from scratch.
Once you have your branding it's time to build your store! I recommend completing this free course by Shopify Compass. It's broken down into easy steps and will show you how to design your store, launch your store, and create happy returning customers.
I hope this helps, if you have any questions please do not hesitate to sing out here. I'm very excited for you and your new venture!