@Krumple,
To say that one is a God is to say that (at least) one is omnipotent (does what he wants chooses to do), omniscient (knows everything), and omnipresent (can be everywhere at once). Logically, no human on earth can be a God in their own right because they lack fundamental qualities essential to the predication of a "God."
Many philosophers have attempted to explain purpose and independency from God (and in the absence of) on free will. Ironically, most theists would argue against the (wrongly attributed to all theists) popular conception that God controls respects in all respects. Since the middle ages, many theists have argued that God occupies a place outside our specific time. If he did, God would violate his own predicates and he wouldn't be a God. Most theists believe that God is more of a bystander than anything else, looking in rather than actively taking part. But indirectly, God factors in via faith (a notion of eternity [omnipresent] which he occupies and which we inevitably enter). But in manners of free will, though he has no effect on time and our ability to do X or Y, God is still predicated with omnipotence. Logically, God is aware of all outcomes regardless of the path we take which culminates in access to eternity (Gods omnipresentcy).
With that in mind, if humans have free will, and, as the question asks, what purpose we should have, if I were a God, there would be no other desire than moral and ethical obedience. I have everything else accept that. I am omnipotent, so do not need anything else to do what I want. I am omniscient, so I do not need others to research for me because I know everything. I am omnipresent, so I do not need others to discover for me because I can be everywhere. But moral and ethically, I am powerless under the presumptive measures of free will but self interested in terms of the notion of eternity and your inclusion. Most, if not all, monotheistic religions (Christianity, Judaism, Islam) have this premise, that the action of free will and a rightful path gains you access to eternity. If I were a God and I were complete in every way save your inclusion, wouldn't it be in my interest to include you in everything (Gods notion of eternity).
The purpose I would give humans would be to reunite with me, the perfect being (I have everything)? who is (under this logic) imperfect until you join me in eternity. If free will dictates that either X or Y may be chosen, and my eternity is the end goal, the only thing that is left is your intangible morality and ethics. On that note, you could have and type of morality you wished (it's all relative). But since the end goal is above all a complete eternity, as long as you get there (no one lives forever), its all good. You could be a rotten bastard and still reach a complete eternity. The point of contention for everybody comes from the friction the relative accounts of morality and ethics creates, but it is still the final result?death? that makes a God by its nature perfect in eternity.