/u/Mark_GGG If an aura is supported by both divine blessing and generosity, it is not active on you. The wording on the gem implies that if the aura is not affecting you, then you can have more than one. Does this mean that by supporting auras by both of these supports, you can support as many auras as you like with divine blessing and all of them will apply to your allies?
Secondly, in the image provided for Divine Blessing (at level 20) it states that supported skills cost +233 mana. For clarification, does this mean that the cost to cast the skill is equal to that base cost of 233, or is it equal to the reservation cost + 233?
If an aura is supported by both divine blessing and generosity, it is not active on you.
Incorrect. The aura is on you, it is not affecting you. Those are very different things. An aura is on the thing it originates from, regardless of whether it is affecting that thing.
Secondly, in the image provided for Divine Blessing (at level 20) it states that supported skills cost +233 mana. For clarification, does this mean that the cost to cast the skill is equal to that base cost of 233, or is it equal to the reservation cost + 233?
The 233 is not a base cost, it is an addition to the base cost. A Reservation is not a Cost. The gem changes the reservation to a (base) cost, and also has a modifier that adds to the cost.