Lighthouse would be a good one to use. You want some sort of defense against attacks to be available, and lighthouse is an obvious one, and it's also clear why it's a duration - it protects you while it stays out!
Cutpurse is a reasonable attack to use. It demonstrates how attacks hurt, but it'll never be too bad because it'll never hit anybody's "good cards".
Armory seems fine to include as a gainer (the recommended "First Game" set has Workshop). The gaining on top of the deck doesn't seem like it would be confusing.
Smithy variants are harder to pick - you should probably include one, but the choices are Wharf, Rabble, Catacombs, and Hunting Grounds. Rabble can be a nasty attack if stacked (as it would be with 3-4 players), Wharf is an extra duration, and Catacombs/Hunting Grounds have on-trash abilities whose uses will be sort of obscure. Maybe use Catacombs.
Don't include alt-VP or Kingdom Treasures. Province/Duchy/Estate are already new VP cards in someone's first game, and Copper/Silver/Gold are new too.
How about this kingdom? Worker's Village, Catacombs, Cutpurse, Lighthouse, Armory, Altar, Storeroom, Navigator, Bazaar, Smugglers. No platinum/colony or shelters.
Has Bazaar and Worker's Village as villages with two different benefits. Has Catacombs as terminal draw. Cutpurse as an attack that hits enough to hurt but not enough to cripple, and Lighthouse as a defense against it. Gainer in Armory and Altar, Altar as a trasher. With a few spare slots, I put in Smugglers because that's non-attack player interaction, and people might like smuggling good stuff. Navigator and Storeroom because why not, but maybe there's better stuff to put in those slots. Maybe swap in Hunting Grounds instead of Storeroom, then you'll have two cards with on-trash abilities.