Checking old sales threads here (although many people remove prices from closed threads you can still build an understanding of value after a while of looking at new sales) and on auction and knife resale sites is a great way to determine values. You may ask for advice but you may not ask how much a specific piece is worth.
With most similar things on the internet being free it can at first seem odd that you must pay for a membership here in order to ask certain questions or post certain types of thread. But you will find that this forum is somewhat unique and that paid subscriptions can actually be quite valuable. Especially since you will probably start wanting to buy and sell here if you're really going to get into collecting.
Regarding knife collecting:
My advice is that if you're going to get into knife collecting for the sake of collecting, you should look into handmade, "custom" knives. Production knives are fine, don't get me wrong, and many people enjoy collecting certain brands/manufacturers, but handmade knives (handmade anything, really) is just a whole 'nother ball game. Many people start with production knives, then move to mid-techs like CRK, Hinderer, Strider, etc. and finally handmade, custom pieces. Having the foreknowledge of seeking to create a collection and how much you have to spend/invest puts you in the privileged position of being able to skip straight to the high end should you so choose. You'll also find that high end knives in general have great resale value so you can hone your tastes without losing too much.
If you're interested in production knives, decide what it is about the company you like first or else you'll find yourself with a bunch of knives you don't particularly care about and aren't attached to wondering what the point was. With Benchmade for instance, do you like the cool materials used in Gold class limited editions? Spyderco regularly collaborates with great designers and they do a lot of 'sprint runs' of their more popular models with cutting edge steels (pun intended). Great Eastern Cutlery revives classic brands and patterns with incredible variety and top notch F&F.
Finally, welcome to the forum! You'll find tons of great people and sub-communities, stunning works of art and craftsmanship, you'll laugh, you'll cry, you'll go broke. Cheers!