I would go for a more end-of-the-Han-era style feudalism, with some changes. First, I would gather my forces. At first it would be any public servants and any and all military forces I can find. After having brought them under my wing, I would make the Portland area know that a new protection force was established. Then it would be all out war with the gangs until I could get leaders to have a sit down. At this sit down I use a carrot and stick routine to get the gangs to settle outside Portland. I take over the city as the gangs set up vassal states. Once take-over is complete, I'd start public improvements again, and open enlistment stations. After the people warm up to me (the gangs should be at least set in their settlements) I will start conscription, and soon after instate mandatory military service. Once the gang states rebel ( I know it would happen, it's their nature) I use the large army to crush resistance. After defeating the gang lords I would recruit most of their members into my army. I might keep one gang alive, to eventually transform into a policing force. The vassal states become provinces/municipalities/counties, and I instate new nobles there from my close advisers. After gathering a large military force, I would crush any resistance in Oregon. I mean burn and kill and force to join if you resist. I would establish myself as fucking rex imperator, and there would definitely Big Brother-esque posters. After this reign of fire, I would establish more provinces, instate more nobles, and then turn to public improvement across the land. During this time I would feed recruits into the new police force, who in turn would take care of many responsibilities for me, namely keeping criminals in check, seeing to public improvement, patrolling the borders, establishing prisons (they'll get funding), and work gangs. Using the work gangs and conscripted and voluntary civilians, I would build fortresses and castles. The police force would also hold the judiciary system within it. And to top it off we will distribute the law in poster form throughout the country.