This is generally regarded as the best military turn-bolt rifle ever made. The .303 British cartridge you can generally find most anywhere. Check your local gun shop. See what's on sale, what's in the used department, and ask for advice. A Russian or Chinese SKS rifle is another inexpensive possibility.
Prices seem to be going up, however.
Ammo Blackhills Ammunition makes the best ammunition, or so I hear. However, it's probably cheaper to stock-up on military surplus ammo which your local gunstore will frequently have at amazingly low prices. Sometimes this ammo is in poor condition, sometimes it's factory-new. Hornady also makes excellent ammunition. The editor of Fighting Firearms magazine highly recommends the Hornady Custom pistol ammo loaded with the XTP bullets.