All jewels are available in Cash Shop. Also, you can get them by killing bosses and participating in daily events, more information about boss & event rewards can be found here.
Jewel of Ancient Harmony
This jewel gives the possibility to add Harmony options to Ancient Items (works with regular items as well). Option is picked randomly according to the item level and will be set to the maximum possible parameters, so there is no need in Refining Stones when using this bad boy. Jewel success rate is 100%. More information about Harmony Options can be found here.
If your item already has Harmony option in it, jewel will randomly change it to another, so you might need a certain amount of those to get the specific option you desire.
Jewel of Luck
This one is pretty self-explanatory - it gives the the possibility to add Luck option to any item (except the ones, that can't have that option by default). Jewel success rate is 50%.