I too started on a mini-14. Being in CA, it is one of the easiest centerfire semi-auto rifles to have, and can do just fine. I shot SMM3Gun last year with one. It burped on me a few times (stuck mags, double feeds) but I also hit a 300ish yrd bonus strobe target with it (Tac Iron). Some mini's are accurate, some are not. The tolerances are different for each one (gas piston, barrel harmonics, stock bedding, ect.) You can shoot one for all that it is worth, but to upgrade the accuracy or any other parts of it is not worth it with quality AR type rifles around. I am now building a 3 gun AR (JP Lower and BCM 18" upper) just because I would like a rifle that I KNOW is a better shot than I am.
If you plan to get into HM at some point, and want to shoot a M1A, than it is good practice with the reloads, and the manual of arms is reasonably similar.