If you want soft lighting and a lack of reflections, use a tent.
There are all kinds of elaborate setups for this, but I find
that a roll of computer paper or similar works fine, just roll a
cylinder and place it around your jewelry standing up vertically.
See how a cylinder works, make a cone if you are bothered by
reflections (look in your viewfinder) from the camera or near the
camera axis. In this case you will have to trim the edge of the
paper to it to get it to atand up straight. My advice for
lighting would be to use a little “cigarette pack” flash out of
the junk drawer at your local photo shop on a cord so you can
move it around. I would start by holding it at two o’clock
relative to the jewelry and experiment. You can also use more
than one flash if you have a way to mount them and a slave unit
to get the first flash to fire them. You might find a slave unt
in the junk drawer, too.
If you get picky and need specular reflections (points of light)
for stones or highlights, you can cut holes in the tent and angle
the flash to get both diffuesd and direct light from one source.
Hold the flash so it has a direct line to the jewelry through the
hole, but hold it far enough from the hole that it also diffuses
through the tent. You can get your lighting right by making some
experiments on cheap color negative film. Just try different
distances from the tent for your flash. You can hand hold the
camera, glide into focus position and trip the shutter while
holding the flash at the right distance in the other hand . . .
easy with a little practice, I have the photos to prove it. The
flash probably has a Guide Number of about 45, so try eighteen
inches from the tent with 100 ASA film. regardless of where you
start, if you halve and double the distances from a few inches
away to a few feet, after a roll or two you will have your
exposure right. Remember you will need a different distance for
the flash for each camera distance from the jewelry.
If you need something more sophisticated that this, you can poke
your camera through a cone or floodlight reflector and bounce the
flash from down by the jewelry back up at the reflector at about
a 30 to 45 degree angle. If your lens is long enough and it has
a hood on it, you won’t get flare at the lens. You can use a
couple of light sources, as described, and even put little
mirrors into the reflector for bright spots. I haven’t tried
this setup, but I’ve seen it described, with the (good) pix in
Kodak publications. Well, that’s more than you ever wanted to
know about this, right?? Next thing is, I’d try to upgrade the
lens, and there are some cheap ways to do this . . . . . .