Gem Gifting Rules??

Can someone please explain the intricacies of gifting gems to friends?

First off, I've been playing this game for a while (lvl 34) and I've searched and can't find anything beyond the basics, but I still can't wrap my head around it.

There's this so-called "24-hour" rule, but it doesn't seem to play out that simple in the real world. When I gift my 6 gems to 6 people ... 6 more gems are available for gifting in only a few hours; however, not to the same 6 friends, which are greyed out. I resist using the new 6 gems immediately thinking that if I use them, it will take ~48 hours until I can gift again to my consistent circle of 6 friends.

So I wait. But it doesn't seem my greyed out 6 friends become available in 24 hours. This is made very clear as I gifted the same time I started a colosseum event - but long after my event is over the next day, my 6 friends were still greyed out. It even appears that they are sometimes greyed out for almost 48 hours. This makes me feel horrible as I don't want my friends to think I slacked-off that day.

So is this "24-hour" rule assuming the receiver logs-in every day & accepts the gem? What if you gift a gem every day for a week to a friend who doesn't log-in for a week? Does he receive 7 gems as soon as he logs on again?

What if you want to gift a friend, but 6 others have already gifted him that day? Does he appear greyed out to you or does the game allow you to gift to him, but it just gets wasted & he never knows of your gift?

Thanks.

p.s. add me: BonesDT