We have no control on limit of how many gifts/invite you can send per day - it's controlled by Facebook.
Our limit was capped due to high number of blocks and lower accept ratio. Below is a quote from Facebook explaining why the sudden drop:
Current Status: Allocations bug resolved
We've located a recent allocations bug that artificially boosted app allocations over the past few days. We've resolved the bug now, and this may cause a distinct delta in the number of allocations your apps have available to them. The number of allocations for your application bucket (specifically requests) will return to its previous levels. Thanks for understanding!
Please help us to raise limit by sending only to friends that will likely accept your invite and gifts.