The best price I've found for these (online) is
http://www.stampnmadness.com/
For example: a set of 24 costs $38 at my local stamp store. This site has the same set listed for $30.50. Her "sale" price is her everyday price according to an e-mail I got from her.
It was suggested to me that you start with 12 packs if you can.
There are 84 colors currently and that's the easiest way to get them all.
I heard that there are 12 new colors coming out some time this month or next.
I buy the 5g jars. They last a long time.
Here is the site for the company that makes them so you can see the color combos:
http://www.luminarteinc.com/catalog/twinkling-h20s.html
I really do love mine - I'm only up to 60 colors. GOT TO GET MORE!!