Thanks for your answer, Blue Jay. If the correct one is "I'm on my 14 carats/I'm 14 carat", could this possibly mean that she's currently wearing her 14 carat gold thingy to such an extent that she is 14-carat gold herself? In other words, could the use of "on" imply the fact that she's wearing the gold at this time but that she might change into something else such as a diamond,
To me, it wouldn't make sense to say I'm on my 14 carats, so your guess is as good as mine. I'm in... and I've on...would both make sense, though, and would have similar meanings. Neither would require her to be completely covered. You could say She was in a bikini, or She was in heels. This is speculatio