I started playing back in 1994 with Unlimited.  Didn't spend a lot on cards at the time, then skipped Arabian Nights, Antiquities, and Legends, picked back up with The Dark, and played consistently up through around 2004.  

By 2002, I'd acquired, relatively cheaply, either cash or trade:
Black Lotus, Mox Jet, Mox Pearl, Mox Sapphire, Ancestral Recall and Timetwister (2/3 of the Power 9)
Library of Alexandria (at the time, the unofficial "Power 10" card)
Playsets of the following dual lands: Badlands, Bayou, Plateau, Savannah, and Underground Sea.
Multiple copies of the following dual lands: Scrubland, Taiga, Tropical Island, and Tundra.
Complete Set of The Dark
Playsets/Multiple copies of Power Artifact, Force of Will, Lion's Eye Diamond, Tolarian Academy, Yawgmoth's Will, Grim Monolith, and Memory Jar.
Individual copies of Mana Vault, Wheel of Fortune, All Hallow's Eve, Concordant Crossroads, Lake of the Dead, Vampiric Tutor, and Gaea's Cradle.

That list of cards, in today's value, is incredible.  The P9 were all Unlimited but the Black Lotus sells on Card Kingdom for $26K, Mox Sapphire is $9500, Ancestral Recall is $8500, Timetwister is $8K, Mox Jet and Mox Pearl are both $7500. 

Revised dual lands are as follows: Underground Sea is $1000, Tropical Island and Volcanic Island are $900, Bayou and Tundra are both roughly $625, Badlands is $525.  Taiga, Savannah, and Scrubland are all roughly $385. Plateau is the "cheap" one, at $325 per copy.

Library of Alexandria is $6300.

The rest of the cards I listed range in price, per copy, from $90 (Mana Vault, Memory Jar, Vampiric Tutor), growing to $150 (Force of Will), making the way to $200 (Lake of the Dead, Tolarian Academy), bouncing to $250 (Concordant Crossroads), climbing to $325 (Yawgmoth's Will), hitting $400 (Grim Monolith), passing $500 (Power Artifact and Wheel of Fortune), skipping past $700 (Lion's Eye Diamond), cruising to $800 (All Hallow's Eve) and topping out at $1100 (Gaea's Cradle).

The set of The Dark is valued at approximately $1800 today.

These are just the REALLY valuable cards I owned.  There are simply too many others that sell today for between $40 and $90 to list.  Above is literally over $100K in cards that were in my possession in 2002.  I had sold all of them by 2005 for approximately $900 (I got $60 for my PLAYSET of Underground Seas, a figure that would be $4K today.), except for All Hallow's Eve, which I hung onto for another 8 years or so and sold for $300 (it had been a birthday gift in 2001 from one of my college roommates and frequent play partners, as he knew I had wanted that card for a long time and made some trades to acquire it for me), but it was just sitting in a binder looking pretty.  

Sure, hindsight is always 20/20, and I had ZERO way of knowing if the game would still be published or produced 15 years later.  I was not playing much if at all at that point, as the gaming opportunities in my part of the city had hit a rough patch, so it was not viewed as a loss at the time, but still:

My kids' college would be paid for.  My mortgage would be paid off. I'd own a Werewolf by Night #32.

This is why I won't sell these "hot" comics.  Partly because I cannot be certain I will be able or willing to pay future prices for them, especially if they don't drop back down, and partly because I got burned once by dumping things I didn't think I would care about again but would love to have today, some to simply sell at their current value, and some to keep for play purposes (Commander is SO much easier when you have dual lands, and I would really love to have the Gaea's Cradle for my elf deck and the All Hallow's Eve for my graveyard reanimation deck).

Probably far more than you EVER wanted or expected to learn about my history with Magic, this evening or ever. 

I've tried teaching my daughters, and while they like the game, they're not rabid about it.  I had made some inroads with my neighbor across the street early last year, as I found out he and his sons play, but then COVID happened, so that went nowhere. 

I actually told my wife I'm at a crossroads right now with my collection.  My favorite shop to play at is 30 minutes away, and I only get up there once a month maybe.  The last few sets have been underwhelming for me in terms of interest (the last one I really enjoyed was Throne of Eldraine, but Ikoria held zero appeal, Zendikar Rising was OK, Kaldheim isn't really my cup of tea, and Strixhaven isn't grabbing me yet, although I may give it a chance with a few drafts).  There are specific cards in each set that I want for Commander, but I'm not running out to buy a box when I only really want 3-5 cards from the set.  I do buy some of the set-based Commander products (I got the Elf deck from Kaldheim, primarily for the face Legend and the Wolverine Riders, along with some of the other rares), so I'll see what comes from Strixhaven in that regard.

So, I'm pondering maybe keeping maybe 6-8 of my Commander decks and selling off the other cards in my collection that I likely won't be using.  I don't play Blue in any deck except my Black/Blue Zombie deck, so there are a lot of blue cards (Rhystic Study, Propaganda, etc.), multi-color with blue (Muldrotha, Yarok, bunch of older stuff when I wanted to build a discard Commander deck) as well as multi-colored lands with blue (Breeding Pools, Hinterland Harbors, Sulfur Falls, etc.) that I could move for money.  There are also a lot of Reserve List cards in my collection that I doubt I will be putting in a deck any time soon, and then I could use the proceeds to buy some older cards that I want (stuff like No Mercy, Oppression, Attrition, maybe some beat-up dual lands just for play purposes).

What I have started doing is collecting specific artists' work.  I have almost a complete set of Seb McKinnon's regular cards and am working on the foils now.  His art is simply incredible.  He's running a Kickstarter right now for a movie he is trying to make, and supporters can get playmats, signed prints, and the like, and he's actually doing a brand-new sketch based on supporters' input that will be available.  You can check out his KS here: Seb McKinnon Kickstarter.  I'm currently in for 3 prints, which will be his Secret Lair version of Damnation, Promise of Tomorrow, and the new sketch, which is a Phyrexian angel figure.

I'm also high on Wylie Beckert, who has been doing work for WotC for a couple of years. His first work was the alternate art for Fae of Wishes from ToE, and he had some in both M21 and Ikoria.  Nothing in Kaldheim, but it looks like he has a couple of cards in Strixhaven.  

I also buy any Alpha/Beta/Unlimited cards I can find on the cheap, along with Arabian Nights, Antiquities, Legends, and The Dark; first copies are put in a binder, extra ones go in the Sell pile.  Oddly, a lot of Fallen Empires and Homelands cards on the Reserve List are hot at the moment and can still be scooped up out of bulk boxes for cheap, so I've making hay on those.  Ice Age through end of Urza's Saga block are also moving pretty well right now as well, so I'd been pounding the pavement hard (prior to getting sick) and buying up lots of rares/uncommons from those sets to fund my other interests in the game.

Looks like Melissa Benson was still doing cards up into the Urza's Saga block but nothing since then. I have a lot of her cards from the Portal/Portal 2 sets.

The Secret Lair cards by and large don't appeal to me, as they're just cash grabs. I did get the cats one they did a couple of years back for a Commander deck (they were adorable), and the Seb McKinnon one was a no-brainer for me. Wish I had ordered both the regular AND the foil (just got the regular), but having one version of them is good enough for now.

Alpha/Beta are particularly hard to find in local shops, but not impossible; I just got a couple, Ironroot Treefolk and Giant Spider, for $1 each last month, giving me about 8 total (most expensive I own are Beta False Orders and Beta Scryb Sprites, both of which are $23). Arabian Nights are probably the toughest to find in the wild; I actually don't own any cards from that set, although I almost bought a collection recently that included a few common cards from AN in it. Antiquities and Legends can be found, even in unsorted bulk boxes sometimes, but they're usually separated and go for a minimum of $1 each; I just picked up a fair amount of Legends for that price from a shop that a college friend of mine co-owns, although I stupidly didn't buy a couple that were grossly underpriced and when I went back, they were already scooped up. The Dark is easier still, and anything after that set is pretty much widely available everywhere.

As I mentioned previously, I do actively search through unsorted bulk bins for collection, but more usually resell. There are a handful of stores around here that just put out boxes of bulk and it's "whatever you find is yours". New Phyrexia has a couple cards that can be found in boxes like that for $.25 apiece (Triumph of the Hordes and Noxious Revival) that I can get upwards of $9 apiece for from Card Kingdom, where I buylist my findings. Twice a year I make a trip to Grove City, PA to hit up a comics/gaming shop there, as the owner buys lots of collections and just puts the boxes out unsearched; I make an entire day of it, sometimes spending 8-9 hours just flicking through piles of cards. It's all very relaxing for me, and since I've made better than $1000 profit each of the past two years doing it, it's worth my time and effort.

I usually take a Friday off from work and go up.  They open at 12:00 (maybe 1:00), so I typically leave home around 10:00 AM, hit one LCS on the way up, stop at the Taco Bell right across the parking lot from the shop for lunch, then head in.

Was thinking about doing a trip later in April, maybe early May.  I'll let you know when I figure out my plans.