The Auto Buff Gem

Is the skill a summon?
Yes: Doesn't work.
No: Keep going.

Is the skill toggleable?
Yes: Doesn't work.
No: Keep going.

Does it have a cooldown?
Yes: Doesn't work.
No: Keep going.

Can you macro it?
Yes: Keep going.
No: Doesn't work.

Does it have reflect?
Yes: Doesn't work.
No: It works with Auto Buff Gem.

Literally every single skill in that list can be answered with those 5 questions. You can complete your table by doing that

You might have misread my post. I'm talking about adding the skill Macro to the skill equip. If you try to add a macro with 3 skills that work with Auto Buff Gem, it won't give you a message saying that you can't equip it, but that doesn't mean that you can equip it as Auto Buff Gem only works with 1 buff skill.

I've added at least most of the Adventurers and Cygnus skills, though there are skills with a icon meaning I can't 100% confirm if the skill works with Auto Buff Gem.