So I have PCs who want be able to more quickly get a bunch of buffs.
They would like a gem then can cast multiple buffs into then activate later as standard action.
The spell slot is occupied until the spell is released from the gem and fades after 24 hours. (The do not want more spells, just to turn them on faster)
No personal spells
Spells effect only the holder of the gem even if the original spell could effect an area or more then one target.
An example would be a gem that could hold 6 levels of spells of up to 3rd level.
The casters in the group fill it with Haste, enlarge person, and bull's strength and then give it to the fighter.
Several hours later the party encounters a dragon that breaths on the PCs and downs the casters. The fighter spends a round and now gains the benefit of all 3 spells as if they were just cast.