"You can increase a Jewel's level via crafting by combining it with 2 other Jewels of the same level and type, along with some gold. For example, if you craft together three Standard Mind Jewels, you'll get one Fortified Mind Jewel." -Fibus

Sorry, I'm confused here.. in order to increase Jewel's level, we need to combine 2 OR 3 Jewels of the same level and type? The amount required for other Jewel's level would be the same? Apologise for my bad english.