Ground spices deteriorate rapidly, although some, like fenugreek, are so hard that they are almost impossible to grind at home. It is probably best to buy a selection, in small quantities, and grind them a little at a time. One advantage of buying whole spices is that you can roast them before you grind them. You can grind spice in a stone mortar and pestle, or in an electric coffee mill. If using the latter, be sure to keep it for spices and have a separate one for grinding coffee beans.
** Herbs and Spices