If we suppose that there exist, as underlying and pure forms of essence/substance:
- Potentiality
- Actuality
- Necessity
it seems that potentiality should be prior.
If there is pure and infinite potentiality, it can logically (but not necessarily) be followed by actualization. There are questions on why all these potentialities or a branch of them should actualize. One argument would be that the actuality itself is a potential outcome, a possibility.
Necessity might be emergent from potentiality as well, as a set of axioms that could be otherwise, but on the particular instance/branch are fixed as they are.
A key question is: How could potentiality exist in the first place? As the eternal prior? Why not be nothing at all? Is potentiality necessary?
Another approach is to claim that necessity is prior, but this raises greater complications: how does necessity itself exist in the first place (same base question on all posited underlying substances/essences), and as an additional question: why does this particular set of necessary rules exist instead of others?
If we claim that actuality is prior and all else follows out of the initial actual existence, this complicates things even more, as actuality inherits the previous difficulty of necessity and is the most complex of the three. It seems that actuality is the necessary part of potentiality, the end result of the interplay between the other two notions. Necessity without potential outcomes is empty, and potentiality without a restriction/selector is infinite.
There still might be confusion between possibility and potentiality. See Language definitions.