You mention "valuable lessons" a lot: forget about them.
The valuable lessons for new players are known as The Rules
After that you can worry about the kind of things you're thinking about.
I think you'll have trouble with Dark Ages because of this as most cards break the rules in some way.
The Kingdom has 10 piles plus the basic supply (except for Ruins/Spoils/various other cards)
Spending money goes on the table, then into your discard (except Spoils)
Any 3 stacks running out ends the game (except Spoils)
When you gain a card it goes to your discard pile (except for Armoury)
Cards do the things written on them when you play them (except on Trash/Gain/Discard effects)
Trashing a card makes it go here into the trash (except for Fortress)
Each pile has the same cards in it (except Ruins, Knights)
Trashed cards are out of play, forget about them (except for Graverobber et al)
You can't play another card if you don't have any actions left (except for Cultist)
There's bad cards that you give to other people (except Deathcart where you take them for yourself)
and on and on....
With all these I wouldn't be at all surprised if they picked a ton of wrong habits that you then had to correct them over for the next few games, let alone the strategic implications of cards like Armoury that will warp their perception of how good gaining cards is. Normally cards that manipulate the basic rules are adequate complication at first, let alone those that break all the rules.
There's a couple in there that work, Junk Dealer is nice, Sage as mentioned could work, but most I would avoid including Marauder and Fortress - yes those two are simple in terms of what they do, but they change the game significantly from the base.
I would recommend
Masquerade (very fun as it keeps people involved when it's not their turn)
Courtyard
Coppersmith
Upgrade
Trading Post
Baron (for example this looks complex but is very simple to get - discard a shit card for a bonus, right, I get it)
Tribute is kind of fun.
Mining Village obviously
Swindler is probably the safest starting attack to go with.
The Alt VPs could be ok, but be wary of downplaying the importance of provinces.