Nick,
Focus is extremely important in macro. It is recommended that you use manual focus. The first photo is a little out of focus (unless you were going for a "soft" look. The diamond was great...I could see facets. The coin is good and in focus. Next, what is your goal with the image....entertain, laugh, the "wow" factor, color, texture, etc. Background is also important. It shows up, even if you don't want it to!! I just jotted down a few thoughts from the top of my head. Keep at it. Take LOTS of macros. Mix it up a bit. AND, don't be afraid!! Take risks!!
Lee