How can I do my Poké Ball decreases so they appear tighter?
I think you'll enjoy trying what's called the "invisible decrease".

By running through two stitches but not actually making the base of both of them, it tightens up the space and only shows a single stitch. It can actually be challenging to see where the decrease is after it's completed.

From the linked article (there are images included for both right and left-handed users to help if you visit the blog):


  
  Insert the hook into the front loop of the first stitch (2 loops on hook). DO NOT YARN OVER:
  Insert the hook into the front loop of the next stitch. To do this, you’ll need to swing the hook down first so you can insert the hook under the front loop. (3 loops on hook)
  Yarn over and draw through the first two loops on the hook. (2 loops on hook)
  Yarn over and draw through both loops on the hook. Invisible decrease completed
  


As a note, because this is specifically geared towards amigurumi figures, it expects that you're using single crochets. I'm not sure if there's an adjustment that allows this to work with other size stitches.

To compare, here are images that show the three options for decreases. 

These first two images are skipping a stitch and the standard single crochet two together (sc2tog). In both cases, the decrease is pretty obvious.



And here's what the invisible decrease looks like, which is nearly indistinguishable compared to the other two: