Don't bother with the Mini-14. It just isn't good for much. No historical significance for sure, I think Ruger's intended customer was law enforcement. I've shot them and don't like them either.
If you like history and historical arms then the K98 is hard to beat. Check out
www.mauser.org
Mosin Nagants are very cool too and cheap to collect. Never cared for Springfields, though, a bit pedestrian.
Garands are wonderful to shoot and I think they can still be had cheap through the CMP program if you are willing to do the dance to get one.
AR's are easy to build and much cheaper to do it that way. AR receivers can be had for $100-150 and then get a kit for the flavor you like around $450. Assembly instructions are online or get an Army manual for $10 or so. I built a few but sold them as they don't do much for me.
AK clones can be had for $350-400. Get a Romanian SAR1 (AK clone) strip the furniture, remove cheap Russian bar varnish, have metal refinished in black teflon, have AK74 brake installed and you have a very nice AK. I did this....
SKS's are cheap and not worth it unless strictly collecting. If you don't keep them clean they can and will slam fire, that is, go full auto without warning. Ask me how I know....
M-14's are great however they are too damed expensive. They do shoot very well though.
HK G3's are interesting but pricey for a good one. The roller locking mechanisim is neat but the gun is heavy and it tears the crap out of the brass. Don't expect to reload.
I like semi-auto battle rifles myself. The FN-FAL is my favorite. I have built 3 from kits on legal receivers but the kit market has dried up due to ATF changing their BS interpretations of the law. Still FAL's can be had for $800-1000 and the mags are dirt cheap. The history of the FAL is fascinating too. Designed by a disciple of the God of Firearms, John Browning.
If you would like to shoot an FAL or an AK let me know. I can provide both at my range.
RT