There are many different jobs in the gemological field. Retail can be physically brutal with long hours on your feet. However there are many jobs that less demanding on your body. Gem cutting is a very good option. You can find a local lapidary club and find someone to give you a few lessons. Many club members are actually more knowledgeable and skilled than many professionals. They do it for love and not the money although there is money to be made.
Gem cutting can be peaceful and zen-like yet also give you enough math and science to keep the left brain happy. The downside is that it is expensive to start. Equipment will be a couple thousand, used is a bit cheaper but hard to find. Rough can be cheap or astronomical. Stay with cheap until you build your skills. And it will be difficult to make a good living unless you are extremely talented and creative like these guys:
Getting to that level of cutting is an art that takes decades of learning and practice. But you can still cut to the best of your ability and sell them to local stores or at local craft shows. Repair work is low paying and tedious but you might be able to pay the bills with it.
If you learn to make jewelry you can have a very good job. Good benchmen are always in demand. There are several good schools. Check your local college or arts center. Combine cutting and jewelry making and you'll be golden. Better yet...learn watchmaking! Watches are popular with baby boomers but must watchmakers are near retirement. A young person with good training can write their own ticket and have a lucrative career.
You could work in a gem lab identifying and grading gems and diamonds. It is nice, clean, comfortable work. But you will need to get an education at GIA or Gem-A. You can study at home or on campus...your choice.
There are plenty of other opportunities but you'll find them as you get into it. This should give you a little start. I've been at it professionally for >30 years and I still learn new things and find interesting niche opportunities every day.
Good luck with whatever you decide to do.