If you want 30 head, and are new to chickens as your question rather implies. I would buy 30 head of pullet chicks. Chances are, some of those 30 chicks will be roos, but not 50% as the above poster pointed out if you are hatching your own, and sometimes, I have had 7 out of 10 be roos!
Then within 6 months you are up and running and getting eggs. When you have 30 hens, you have plenty of eggs to incubate, might even get a broody hen or two, but as stated above they are chancy, but do take all the work out of incubating and raising the chicks.
I will tell you, that I have a flock of 10, sometimes as high as 18, sometimes down to 5.... but I have been at 10 for a long time, with one roo, and they give me enough eggs, but it depends what you want to do.
my point is, it would be better to buy the pullet chicks and get started, and then maintain your flock, and begin work on breed quality and genetics for good builds and egg laying.
just my 2 cents
mk