Depends upon your circumstance. The Mini-30 is reliable and benefits from cheap ammo, but the mini-14 and 30 are not known for their accuracy. I personally have settled on a .30 caliber cartridge and use the M1A in .308. A rack grade rifle is easily capable of 3 MOA accuracy (15" @500 yds) with iron sights and surplus ammo. Hornady's 110 grain TAP ammo is a good choice if you are worried about over penetration, and the rifle is brute simple and utterly reliable. They cost 3 times what a Ruger does but are worth every penny. Get a copy of Boston's Gun Bible from Javelin Press for the most thorough evaluation of battle rifles and battle carbines that I've ever seen.
Sorry, just noticed your cost caveat. If you go with a Ruger, get one in .223. More and better ammo available, magazines easier to obtain and ballistics are better.
I was going to argue with you over that, as my M1 cost just under $400.00, and then I looked them up on CMP. Wow! I should have bought ten, or twenty of them 15 years ago. ;)
Get a copy of Boston's Gun Bible from JavelinPress.com for the most thorough evaluation of battle rifles and battle carbines that I've ever seen.
A lot depends on the range you are looking at. If you are out in the boonies, the M1-A (civillian M-14) is good to 700+ yards, as far (or farther) than most can shoot). In town, it is usually under 75 yards to the next building, and the mini is more than adequate with an effective range in .223 of 300 yards.
Most East bloc rifles, such as the SKS and AK variants will also handle that range envelope and may be ideal for a limited budget.
Fancy tackdrivers are nice, but you want reliability and something which will consistently hit inside a 6 inch circle at 100 yards (smaller is even better).
Always keep in mind that there is something on the other side of whatever goblins you may be firing at, and a rifle may not be the best choice.
Consider a rifle in a pistol caliber such as the Hi-point in 9mm or .40, or even a lever action in .357 or .44. Marlin lever rifles have been very accurate in my experience, and with practice are almost as fast as a semi-auto for the first 10 rounds (reloading is slow).
Also consider a shotgun if your area is one of closely spaced homes, just to keep from wasting a neighbor you don't want to. You are responsible for what your rounds hit downrange, too.