When it comes to fishing tackle (as with many collectibles) it's all about condition, rarity, and age. It's best to spend more on one hard to find lure that's in great shape than to spend the same amount on several lures of lesser quality condition. Finding the original box is always a big plus. And whatever you do, don't try cleaning or restoring them.
Invest in good reference books and read them. I would suggest-
Fishing Tackle Antiques and Collectibles: Reference and Evaluation of Pre-1960 Tackle by Karl T. White
Also- Old Fishing Lures & Tackle: Identification and Value Guide 8th ed. By Russell E. Lewis, Carl F. Luckey
and/or- Fishing Lure Collectibles: An Identification and Value Guide to the Most Collectible Antique Fishing Lure by Dudley Murphy and Deanie Murphy
Or any of the books written by these gentlemen. You will know much of what can be learned from books on lure collecting. You'll have to invest time (and money) in something if you want to become proficient at it.