Yeah, you should pick a credo for something you can do the quests for.
Gems appear in areas, so if you found a diamond somewhere you could dig out more tiles in the area and find more diamonds. The closer to the surface you are, the fewer the gems. As you get deeper though these areas will have more and more gems.
Here is a place from W10, level 5 that had an overlapping jade and opal gem node, and I paved every spot I found a gem.

But on level 1 there would probably be only 5 gems in the same sized area. So for gem hunter, you want to wait until you have a deeper, more developed mine and several different locations of different gemstones. It will be much easier then.