Hmmm... Well first welcome to JediDefender.com of course.
As far as how you learn to collect, you really only learn this hobby by jumping in and getting your hands dirty. If you want everything, you just start looking and buying everything you want as you're financially capable. Issues of grading figures on your own are simply learned by experience... You pick the pegs over till you find the quality you want or as near as you can find. If you want to upgrade it down the road because of a "flaw" you try to do so...
Grading modern figures I liken to putting expensive rims on a $2000.00 car. Also "you can't polish a turd" comes to mind as an applicable phrase... So going to a company like AFA to grade your POTF2 Green Card Luke Stormtrooper just isn't smart collecting IMO...
I personally don't view card grading as a smart investment for vintage collecting either. I collected vintage since I was in my teens and for me I prefer using my own eye, hands, and knowledge of the vintage hobby to grade toys rather than relying on the flawed opinions of companies like AFA or whatever that other one is that you mentioned. Those people half-ass the effort and you pay more for someone to basically "do the hobby" for you.
If you want to be IN the hobby, especially vintage, you look at the free vintage resources on the net like stuff Gus Lopez has up for instance... You learn what's good, what's fake, and whatnot... You hang out at a good vintage forum, and might I say that our vintage forum has very knowledgeable guys like our own forum mod DSJ (Dale) there to give advice.
Vintage is something you have to maybe read up on more to really learn it, but modern you pick up mostly just by visiting a site like here at JD.com and get involved in the community...
Bare in mind too that "C9+" varies by every dealer/seller... One guy may think a C9+ Vintage Loose 3PO is one that when you move his limbs you hear the snap of the paint sealed on the plastic... Others may say that just a 3PO without flaws on the gold and whose limbs don't flop around loosely is C9+...
And worrying about what's "rare" isn't wise unless you're looking to get into something for financial reasons... With vintage, rares will pop right up when you start looking at what stuff's selling for on Ebay... When you see the difference between what a Hoth Soldier sells for compared to Amanaman, or how a Luke Skywalker sells against a double telescoping saber Luke Skywalker.
With modern, buying based on value probably just isn't going to earn a lot of friends in the hobby... Collecting because you really want this stuff though, that's what the community is all about. And not to mention that what's "rare" in the modern line is generally not actually rare, and it's more just something that will decrease in value real fast down the road. Thank God... I like the hobby not having value. That makes me feel less dirty.
