From your previous post (2/8) I assume you are looking to an export market in the West (US and Europe?). Perhaps retail? Beyond this, IDK what your “target groups” would be. When you ask someone to feed you design ideas, you are pretty much asking someone to share their creative products with you. Why should another craftsman share their design ideas with you. You could certainly employ someone as a designer for your production shop. If you are mainly interested in manufacturing what sells (as opposed to some artistic product that it satisfies you to design and produce), you could look at ebay, which allows you to look at sold objects (only sold) and completed sales (both sold and unsold, which tells you what percentage of a type of object is selling). A tech savvy person may be able to tell you how to access traffic data for sites which would tell you what sites sell a lot or at least those which are visited a lot. If you are looking for high volume products to sell, perhaps this kind of tech data would work better for you than asking for actual designs. The Chinese copy everything and sell it cheaper than the originals and you can do the same.
You could also look at Etsy and research what is selling there to millenials, etc. Or look for items which have few sellers. If you can design something unique and beautiful which no one else is selling, you can create your own market.
As to the best online marketing strategies for startups, there are books and books written about this and even some targeted specifically at the craft jewelry market. It would be easy enough to find and buy some of these and read through them From what I’ve heard from friends lately, there is a lot of traffic on Facebook and Instagram and similar sites for sales. If you can get a lot of likes and views, that will probably translate into sales, but, again, there are websites and books about this which you should look into.
A lot of folks on here are more interested in creating what they like and then finding a way to sell it than they are interested in finding high volume items to reproduce, which seems to be your focus. It seems to me you need help with marketing rather than jewelry designs, and, as I say, there’s lots of literature on that. As you get going, the book, The Four Hour Work Week might also be something to look at, as it’s a way to make money by assembling a network of people to do the work and then managing them. Hope this helps.