I've seen many new Hydro growers learn the hard way that you do not want a very large tank or resorvoir..like 30 gallons is way too large...more water = more work.....I suggest a 8 gallon tank, with 6 gallons of water, and either 4 or 5 or 6 grow cups.
If you do not use HID lights, or IF you DO have A/C, then you do not need a water chiller.
I start with seeds, and use a 6 cup tank. I ALWAYS get 3 female and 3 females so I have plenty of room for the 3 to Flower. Often I remove one or two and put them in a 5 gallon bucket and I have had two in one 5 gallon bucket. It is fine for the roots to tangle and fill up the tank. That is no problem.