Well, what I would do in this situation is very complicated. Since the beginning years will be all chaos and anarchy, I would set out to find a small group of allies and we would all set out and do our best to help each other survive. With the deaths of all the weaklings, I would gather up many survivors and create a clan with a sort of oligarchy. With everything within my area in peace, I would then create and Army, for the defence of my people and the destruction of my enemies.
With arms, I would then instigate a smaller weaker rival to go to war with me and crush them, taking all that was once theirs. I would also do my best to forge as many alliances as I can, while making sure to strengthen my alliances with those I can trust and breaking off alliances with those I cannot trust. Of course, I would also establish trade rights for the benefit of my clan's treasury.
With the first decade or so finished, I would then gather up my most trustworthy of allies and we would form a larger stronger clan, so we could be a super power on the island and not easily conquered. With that in mind, my rivals would also do as such and there would be a handful of these Mega-Clans.
Inevitably, war would start between a few of these Mega-Clans and I would my best to keep my Faction out of it. If I were to get involved however, I would do my best to use the Guerilla Tactics that I am so fond of to my advantage and win over my foe. After the inevitable victory of one faction or the other, if I were to lose, I would go into hiding and start a rebellion. If I were the Victor, I would do my best to rule as justly as possible. I would make sure the small female population was taken care of and put those I deem worthy into my Harem and thus ensuring my Lineages survival, so they may rule as I did and everyone would live happily ever after.
I'd try to do something like that anyway.