Generally it is best to throw a list together for us to critique than for us to write one for you. There are a lot of different play styles and opinions here
What kind of army would you like to field? Based on your models, you can't run the new warhost options, save for some formations but might not fit into 600pts. Why are we limited to 600? What about 1k or 1500? You will have to run a CAD either way.
A farseer, 2x guardian defender squads with platforms and a Warlock and a unit of Avengers with a wave serpent is a good place to start though.