Minecraft wiki entry for Dripstone_farming, associated text: Pointed dripstone on its own takes 5 real life days to grow, so it is almost unable to farm on its own. If you place water above the block which the pointed dripstone is growing on, it will grow slightly faster. However, it is still almost unable to farm in that way, but if you make the block it is growing on a dripstone block, it will speed up to about 100 minutes per stage of growth, and it will also produce stalagmites on the floor.
You have a 1/4 chance to be able to buy 4 dripstone blocks for one emerald from a stone mason in Bedrock Edition, and in Java Edition the chance is 2/7.