You're about a month late in getting cheap 223 ammo. If your intentions include shooting over 150 yards, you'll need a centerfire. The minimum I'd suggest would be a .223 Rem but the AWB panic has run the price of that ammo over double what it was 2 weeks ago. Other common cartridges that would be suitable are 243 through 308 Winchester. The .308 is always a good choice for target or hunting medium sized game.
Rifle brand options would include Howa, Savage, and some versions of Remington 700. Heavy barrelled target/varmint rifles usually allow more shooting with less barrel cooling time on the range.