Thanks for your PM Hannah, I'll reply here.
You can make a case for any of these lenses. For serious macro, either the 100 or 60 would be my choice, probably the 100. Except that it's a lot heavier (really needs a tripod collar - you can get one, but a genuine Canon one is about £100
) and it's really a bit too long for most portraits. 60 is perfect for portraits on your camera, then your 18-50 2.8 is pretty good for that also.
Heck, you could even do a pretty good job of both portraits and macro with a supplementary close up lens for £20, or a Raynox DCR-250 for £40 - those are kinds of decision only you can make. Depends what you're doing and how critical you are.
Here's another one for you, which in your position is what I'd do, putting the emphasis on portraits and creative use of shallow depth of field - Canon 85 1.8 plus a set of Kenko extension tubes for an extra £120. Low risk, both very popular items in the For Sale section. Or, how about this cute little jobbie - new Tamron 60mm f/2 macro, £440
http://www.warehouseexpress.com/buy-tamron-sp-af-60mm-f2-di-ii-ld-if-macro-lens-canon-fit/p1032704 I've never even seen one but I like the spec and I'd be amazed if it's anything short of excellent. F/2 is fab for portraits. I'll stop confusion things now, but I'm liking the 85 + tubes option
Either way, a ringflash is a very good idea for macro. The problem with macro is that you obviously need to be close, which makes getting decent light on the subject physically quite difficult, and depth of field is so shallow with macro that you need high f/numbers. That puts you straight into longer shutter speeds, too long to hand-hold generally, so rather than use a tripod and all the hassle that entails, ringlash is a very popular solution - solves both problems.
I like my RingFlash Adapter thing. I use it more for macro than anything else. If you've got a decent gun, and everybody should have one, it's so easy. Plus, because you're using a normal flash gun which is vastly more powerful than any ringflash, you can use it for portraits and get that distinctive fashion look.
For the price of that Coco jobbie, it's got to be worth a punt for what you want to do. If you want to get creative with macro lighting on the jewelry, use kitchen foil around the ring to moderate the power and direction of the light. Blob of BluTack is fine. The foil will reflect light back into the ring so it's not wasted. For a neater job, it's really easy to cut a couple of pieces of card, back them with foil, and attach them with spots of velcro in any position you like.
HTH