Big Mac's comments about the Mini digesting just about any ammo is right on. Also, if you want hi cap mags, let me suggest you purchase ONLY the PMI (Precision Mag) 20's and 30's. The 40's work very well, but are quite unwieldly. The PMI mags were sold in the '80's under the Federal Ordnance label, with the same part numbers and similar packaging.
RAF's comments about stock, I agree completely. The action should be a force fit into the stock. I found that my group sizes were cut in half (from 3"-4" down to 1"-2") when I switched from the original loose wood stocks to the tight fitting Choate pistol grip synthetic stocks.
IF you want to scope a Mini, you can put on an aftermarket mount, such as B-Square's, but the operating rod will strike the front of the receiver, and the shock will destroy reticles faster than you can ship the scope back and forth. With a regular Mini-14 you MUST fit a rubber buffer.
For scoping, the Ranch Rifle model has a built in buffer (which looks strange but works) and is the way to go. However, if you want to use a red dot type, most of which are 30 mm, you will have to purchase special rings from 30 mm Millet rings that are made for the Mini-14 Ranch.
For mounting the head's up type sites, you might be better off with the B-Square mount (weaver rail) on a regular Mini, and putting a rubber buffer.
Stainless is the way to go.
(Edited to add) And though poor parts support from Ruger (they have them, just don't want to ship directly to us peons) is a minus, these rifles are very dependable, and go BANG! every time.