I have the same question and i'm working on the answer. Is there a cap to the number of Giftable levels??

My set up is my Main account and 2 new slave accounts that i used the RAF to set up. I have multiboxed 3 mages up to currrently Lvl 24 and have been gifting levels to a shaman on the main account. The shaman is up to 23. ( at 25 i will be able to gift to levels and all the toons will be = again ) If you are doing 3 toons like I am you get what equals out to 1 to 1 on the gifted levels. if you were doing 5 you could be gifting levels to 2 toons. You can not gift levels from all 4 slaves to one toon on the main because the toon recieving the leves needs to be lower to recieve any.