Starting a Space Marine Army?

So far I've got a squad of Terminators and a Terminator Captain and a Squad of five ault Marines I've named my chapter Angels of Ultramar (Dark Angels Green and Ultramarines Blue) My question is what other units should I use to finish up this starter army? (I was going to buy the Black Reach set but I have no use for the Orks and I would rather use the money for a Venerable Dreadnought).