Essentially what you need is mobility cos your T3 wont hold out. The squads who will leave your deployment to claim objectives, dire avengers, combat squads etc should all have wave serpents.
Troop choices are vital in 5th ed so at 1500pts I would advise filling them all up. My usual composition would be 10 avengers, 10 guardians w/ Warlock, 10 Guardians w/ warlock, 5 pathfinders, 6 jetbikes, 6 jetbikes. For me this stuff comes to about 850-900 points so there is a lot left for characters and cool stuff. The jetbikes are great becuase at turn 5 when the game could end turbo boost 24" onto an objctive which could win you the game. Hide them earlier on and just fire your shuricannons and they will kill some enemies.