Among the gangs, the Hawks are new to the town of Civville, but are more respected by the population and receive some great advantages.
The first Hawk objective is to make peace with all of the gangs except for the Panthers. Second, the Hawks will need an additional 2-4 new defensive units in their cities to defend their meager assets. We won't waste time here building gun shops. Now, the Hawks need to gather enough Driveby units (roughly 10-20 should do the job depending on your skill setting.) The hawks need to take the island directly south of them that includes the Panther's main base of operations. Once all of the Panther possessions have been taken, work on taking the island all to yourself (which means clear everybody else off of it.) Now, place enough defensive units on the bridges coming into that part of town so that you can seal it off from incoming land units. This will be your staging base.
Your next objective will be to attack the Crips or where the Crips (the civ that is yellow in color) used to be, depending on whether they are alive or not. That part of town is rich in slummage and can be a great source of new units. Make sure that when you attack, you have enough units to fend off the Police that will no doubt take interest in your new gains.
Following that, you should be pretty well off, and I would advise you to take the rest of the island you began the invasion of. Of course followed by the main commerce island that contains the Police HQ. Once you have taken care of those 3 islands (main, former crip, and former panther) you should have no trouble sweeping up the rest of the town into your clutches.