Given all the limitations you set on equipment and location, you've presented a real puzzle. Add to that the lack of familiarity that many of us will have with your camera, and I'm not sure how many answers you'll get. Here's what I would do, but I'm going to have to make some assumptions about your camera that may not be valid:
1. You want the jewelry to stand-out and not the model, so you need to be sure the model selects clothing that sets off the jewelry without being brightly colored.
2. Since you have to do this outdoors and not with controlled lighting, you're going to have a tough time adding some sparkle to the jewelry with your lights. At a minumum you need to shoot in open shade during mid-day, but if you shoot in the morning or evening you should be able to shoot in the sunlight and that will help.
3. When/if you shoot in open shade, enable your flash in fill mode if possible. This will put a catch light in the model's eyes and add some specular highlights to the jewelry. Make sure the model is not too close to a background object if you do this so you don't cast a shadow around the model's outline.
4. If your camera can be set to aperture priority mode, use close to your largest aperture to attempt to put the backgrounds out of focus. With compact cameras, though, the small lens/sensor and maximum aperture size put you at a disadvantage for shallow depth of field. This means you're going to need to have greater distance between your models and the background and you're going to need to be closer to your models to achieve good background blurring.
5. As for closeups - I think you're better off trying to shoot those without a flash, but I don't know the capabilities of your camera for closue up mode, etc. so I'm going to pass on that questions. Perhaps you're better off just experimenting.
Mark
