I sold my Mini-14 back in 2013 and have 2 Mini-30s now.
Much easier to stock up on 1 caliber of ammo.
Older Mini-30s have always had the heavier .625' barrel and don't have the accuracy issues that the older .560" "pencil" barrel Mini-14's can have.
The pencil barrel Minis are greatly helped by adding a two clamp Accustrut.
Some guys have like their Tapco or other aftermarket mags, but they can be iffy.
Stick with Ruger factory mags, the 20 rounders are best in either caliber Mini.
For the Mini-14, one aftermarket mag that is good in the "O.E." brand.
They are only $14 or so when CDNN has them in stock. They are a straight mag like the M-14. Some guys switch out the followers with Ruger mags, some don't.
For the Mini-30, an excellent mag if you can find them is the 30 round KCI. They are built stout like AK mags.
As someone else mentioned, where some go wrong is adding huge, high mounted scopes, bipods and heavy Tacticool stocks to their Mini.
Keep them light, handy and simple.
Mine all have Burris FastFire III dots on an Ultimak railed handguard.
Not sure is if is frowned upon to suggest other forums, but the absolute best source for Mini discussion and improving your Mini is the Mini section at perfectunion.com.