Love this topic and if we all had a crystal ball many of us would be retired by now answering this question for collectibles and the stock market.
When I was younger and actively collecting comics, I luckily seemed to pick a lot of books that are now increasing heavily in value. When I got back in comics a few years ago, I had disposable income that I didn't have in my younger days and was able to start buying more of my childhood favorites, Marvel Silver Age 12c comics. Wish I had bought some more keys but happy with my current collection.
Short answer that I have found is, you can gather information from this and other related boards out there, don't be disappointed if you miss a couple and some that you do purchase don't increase in value.