Bucko is giving good advice. Get lots of clear and watch for it to go on sale and buy a couple extra pounds. I mix and store mine in my gluid bed cups as well as plastic jars. Some mixes especially those containing glitter are best shaken and dipped. I've bought some premixed colors but mostly mix my own.
Word of advice if mixing your own, buy/steal or otherwise procure some 1/8 and 1/4 tsp measureing spoons. A little goes a long way and it is very easy to overfill your container before getting the color the way you want it.
Also, a stack of 3x5 cards for keeping track of your mixtures. I pre number my cards, nn-001, nn-002, nn-003 etc. I leave a line for a color name although that often eludes me. The following lines are used for tracking my additions. First line is always clear and I start with 16 parts (1/8tsps) then go from there. Since I make my own PC cups, I use a sharpie and write the # and description on the outside of the cup and make a color sample which is glued on right beside the description. I use some spinner blades and PC for my sample. (BTW it helps to precoat them white and cure those shiny glades make the color look great but jig heads somehow never turn out the same.)