Unfortunately these common stamps are not gemstones. The "precancels" (top and bottom rows, canceled with the town and date before being attached to the envelope) can be purchased in volume (10,000) on eBay
at 2.5 cents each. The middle row stamp types can be purchased in "kiloware" loads at the rate of 2-3 stamps for a penny. Please note that catalogs price these types at 15-20 cents each, mainly to reflect the labor cost of selling you individual stamps.
Don gave you an excellent response.
May you find many enjoyable moments researching and expanding on your family collection.