It depends on how much money you are willing to invest. If you simply want to tumble polish the stones and then drill a hole, the cost is comparitively minimal. If you want to cut gemstones and polish them then you are speaking of some serious money.
The process of tumbling semiprecious gemstone is fairly simple, but the results can be less than desirable. Unless you are considering learning jewel craft, it is better to buy your working material pre cut.