IMHO, the correct optic set-up for the Mini is best based on the Scout rail.

Given that, a red dot of some sort for close ranges, and/or an illuminated Scout scope whose reticle has hold-overs for longer ranges.  QD mounts for both.  Every component, be it rail, optic mount/rings, and the optics themselves must be carefully chosen to ensure that the line of sight through the optics is as low as possible, so as to ensure a quick, natural, repeatable cheek weld.

I've tried everything else, and the conventionally-mounted scope has never worked well on the Mini.

ETA, the above advice also applies to the M1 Garand, the M-14/M1A, and the M-1 Carbine.  There are good, serviceable Scout mounts available for all of them, which take the place of the wooden handguard.  Amega Ranges makes some, but generally I prefer the Ultimak versions, which are distinctly lower, and that is of paramount importance as explained above.

The Choate HG would be a nice addition, but a vastly more useful accessory would be an Accu-Strut: http://accu-strut.com/.  This device is a MUST on all Minis with the possible exception of the new units with the much thicker barrels.

Their accuracy tips are well-worth reading; all are worth doing, as long as your barrel's muzzle has not been damaged by improper cleaning, such as caused by using a non-coated rod without a muzzle guide.  In such cases, the barrel must be either 1) re-crowned (minor damage), 2) counter-boring (moderate damage, and barrel replacement (severe damage).  Tips:  http://accu-strut.com/pages/accurizing.htm

They do not mention the relatively new approach of modifying the gas port.  The Mini has a replaceable gas orifice contained within the gas block assy.  Dismantling the gas block gives access to the orifice, and the replacement is straightforward.  Since the OEM screws are usually staked, replacement screws should be in-hand prior to making this alteration, and the proper in/lbs torque wrench.. Great care should be taken to ensure that the gas block is installed centered, and with an equal gap on both  sides.  This mod reduces the distance the cases are tossed, and serves to increase bullet velocity since a bit more gas is available to propel the bullet, as opposed to operate the action in which some believe is an unnecessarily violent manner.  OTOH, this makes devices like the Accu-Strut even more useful, as more gas behind the bullet makes for more barrel whip which is tamed to a great degree by the Accu-Strut.  

Since the Mini's trigger group is of the Garand design, a professional trigger job will generally end-up at 4.5# weight of pull, but with a much cleaner and crisper feel.  IMHO, even a relatively heavy trigger that is very clean and crisp is much preferred to a lighter trigger that is rough.  The user can usually do a little polishing of various surfaces inside the trigger group, and done right such a relatively minor re-working can yield results all out of proportion to the trivial time and expense involved.

I will add one important note.  If you believe your Mini is somehow not up to snuff in whatever regard, send the unaltered Mini back to Ruger for a check-over.  I say unaltered because Ruger has historically taken a very dim view of alterations to their firearms.  That said, they will advise you of the condition of your firearm, and possible cost of repair.  I sent my Mini back to them long ago for fitting of "Factory-Only" spare parts such as firing pins, extractors, ejectors, and so forth.  I complained about the inaccuracy of my Mini, and when I got it back they had installed and carefully headspaced a new bolt at no expense to me.  The rifle shot so well compared to before that I made some further mods, and now the pencil-barreled Mini shoots well under 2 MOA regardless of how hot the barrel might be.

Taking your picture, posted above, as a guide, I would suggest two things:

1) Buy a tight-fitting synthetic stock.  Almost all of them fit the Mini action better than the OEM wooden stocks, which are notorious for being ill-fitting and so decreasing accuracy,  The Butler Creek folder is attractive, IMHO, and

2) Buy and install a Choate flash suppressor Front sight combo.  This will add a flash suppressor, which the short-barreled Mini desperately needs, and will also add some barrel-whip dampening mass exactly where it is needed--at the very end of the barrel, and such will definitely help in the accuracy department.  The much improved, military-style winged front sight is an added bonus.  A must-have, IMHO.  http://www.riflestock.com/store/do/product/07-07-22

I imagine that the shims were installed at the very rear of the trigger-guard; the part that actually touches the stock. At least that is where most folks find such most useful. Plastic shims have the advantage of not compressing as wood will do.

The reason I suggested a synthetic stock is that the stock itself will not change dimensionally, as will a wooden stock. A bedded synthetic stock, all other things being equal, is superior to a bedded wooden stock as the wood underlying the bedding can, and will compress over time. Some High-Power competition shooters store their Garands and M1As with the trigger guard unlatched, and so lessening the compression of the underlying wood over time.

One thing you ought to have a look at is the fit-up of the metal stock liner to the legs of the receiver. It is not unknown for the liner to slightly over-ride the legs, and this hardly improves things. If such a thing is occurring, the trick is to remove metal from the portion of the stock liner that contacts the legs. Do so carefully, as the ideal fit-up is the leg butting-up to the stock liner with no gap between them. Remove metal carefully, little-by-little, and test-fit often. The old saying about it being easy to remove and hard to replace holds true here.