My approach has been quite different, partly because my interests are less focused, and partly because I have seldom had the budget to be focused.
So I've always been a more opportunistic sort of collector. Yes, I'll have a general idea what I want when I go to a show. But I seldom end up with exactly what I'd planned on. Some stuff that I like just isn't always there. Like the 60's coke caps in biggish lots for a good price. Sometimes what I think of as a "good " price is a bit outdated.
So I've ended up not necessarily doing research. Of course having collected since the late 70's I have a pretty good overall feel for when something is real or not. I suppose it's been decades of very very slow research.
So a few tips for someone who operates the way I do.
Don't get hung up on getting something in particular. Focus is fine for some things, but don't let it blind you to the really good deal that's right in front of you.
If the item you want isn't rare, wait for the right overall deal. I got down to one card for the 74 Topps set, a Schmidt. At the time they were fairly hot, and there were no bargains. Not a hard card to find, but all the cheap ones were more worn than I wanted. After 3 years I found one that was nice, and about 25% below the usual price. (Of course that was right as the price of that card was heading down so I actually overpaid. )
Don't let a desire to pick up a few items prevent you from buying that one really great item. One show the second table I went to had a drum T206 for 200. (Yes, a long time ago) I wanted it, had hardly ever seen one, and had the money. I passed because I didn't want to buy one card and go home. DOH!
Don't overextend yourself. Sure, if you've got a nice card budget and taking a chance on a card that's 2-300 or more that you're unfamiliar with isn't something that will have any really bad consequences go for it. Anytime you go with the general feeling that something is a good deal or better still is actually fairly rare there's a risk. And even after decades you'll make mistakes. (I just bought an odd pair of stamps for $5 that catalogs about .50 ) As long as that's not taking away from the important stuff just consider it a learning experience and move on. Going from that $5 risk to the confidence to take larger risks has been hard for me to do.
Spend some time away from card shows or the card sections or even memorabilia sections of Ebay. It's not extremely common, but I've picked up a few nice items from other totally unrelated venues.
A Cubs coffee cup that I think is from a team restaurant or something. $2 at a restaurant china show.
A set of oddball advertising cards in the complete promo kit bought at a stamp show.
A nice baseball silk from a coin show
Nice T205 from a stamp show.
If you're only interested in sports stuff, those stops will usually be boring and fairly quick. A friend of mine does three-four fields at Brimfield while I'm only through one to one and a half.
The stuff I learned going to other venues was really useful when I was selling "stuff" on Ebay. It's amazing how easily you can find stuff for a buck or under that will sell for 10-20. It's not always worth the time, but there's also the occasional happy surprise. Finding stuff for 20 or less that sells for 1-200 isn't as easy since there's less of it, but it's possible. The really great pickups will happen too. Like a plate bought for 25 cents that sold for $660
Steve B