First, welcome to the forum- when you get a minute, stop by the intro thread and say howdy.
Next- to your question. HOOOO- Boy! Is that an open ended question or what? Sort of like "I want to buy a car- what should i get?"
First- what experience do you have with firearms? We have folks that come here that run the spectrum from "never shot a gun" to "I build precision rifles from scratch" to "retired member, military rifle team".
Check the net for contacts with your STATE rifle association, and talk with them to see if there is a range in your area that you can visit. Depending on where you are located, you may even hook up with another member of this forum.
Rifles can be divided up by caliber, or by type of action. What you would need for (legal) hunting will vary by state. For instance, Virginia does not permit .223 or 22-250 for deer, Pennsylvania does not permit auto loading rifles for big game, etc.
One that I WOULD suggest you consider would be a .22 automatic. While the ammo is really too light for big game hunting, and would NOT be my first choice for defense, they are inexpensive, ammo is cheap, and a great LEARNING tool. Shop and you can find a good .22 for $200 or less. Used can be very good.
You can then consider rifles such as the SKS, or a good lever action Marlin 30-30, and still be within your $600 budget. The lever action would not be my choice for holding off the 4th Godless Horde of the North Korean Army, but 6 rounds of 30-30 is an attention getter. Standard capacity of an SKS is 10 rounds.
But before we can offer much real advice, you need to do some setting of parameters. Station Wagon, Convertible, or Hybrid?