Re: what gear for pistol/carbine class
Your Mini-14 will run well in class as long as your keep it lubed and use only factory magazines. Don't let the AR15 snobs look down their noses at you. Your Mini will be chugging along when some of them start to choke. Some Mini's do suffer for accuracy or begin to string shots when they get hot. If your's does, check out the Accu-strut.
As for gear, five mags should do. Check with the instructor because most "carbine" classes now are so AR15-centric that all the drills and sets are structured around 30rd mags. No problem using 20's, you'll just reload more.
As for gear. Buy quality and wring it out thoroughly beforehand so you're not adjusting it or fighting it during class. All these include a quality pistol holster (I'm not a serpa fan, btw) and a good rifle sling, either carry strap or three-point. I wouldn't run a single point at your first carbine class.
Some options:
1. Padded battle belt and combo rifle/pistol pouches.
Belt
http://www.hsgi.us/proddetail.php?prod=HSG-SGPB&cat=18
Pouches. I'd get two or three for the belt and pocket the spares.
http://www.hsgi.us/proddetail.php?prod=HSG-DDT&cat=34
Dump pouch for retaining mags. Either condor or maxpedition make good ones.
2. Lightweight chest rig.
http://www.hsgi.us/proddetail.php?prod=HSG-DDTCombo&cat=46
3. Sturdy belt and kydex mag pouches.
I like Blade-tech and Raven concealment, but I'm not sure they make pouches for the Mini-14 mags.
4. Shoulder bag for rifle mags. Pistol and pistol mags on the belt.
http://www.onesourcetactical.com/terroristinterdictionbagtib.aspx#.T6M7FsW6X4E
I've taken or instructed countless rifle classes using each of these methods so I'm confident in these recommendations. You just have to find what works for you.
Don't forget the other incidentals such as camera, water, snacks, sunscreen, ball-cap or brimmed hat, boo-boo kit for cuts, scrapes and burns, folding chair, spare eyeglasses if you wear them, backup eye and ear protection, more ammo than you think you'll need, bug repellent, notepad and pencil, spare clothes for sudden inclement weather, sturdy boots and change of socks, any medication you regularly take or might need to cope with allergies, aches, headache or a sudden cold.
Most important of all is an open mind, willingness to receive instruction and have fun!