Buy an extra coffee grinder (about 20 bucks) to use exclusively for grinding spices. Then buy whole seeds like coriander, cumin, allspice, etc.
Toasting the seeds in a dry skillet for a few minutes will bring out the best in the seeds. Grind them after toasting and you will definitely notice the difference in the aroma and taste of freshly toasted, ground spices.
I use a dry pastry brush to clean out the grinder after using.