Gemstone Caverns, according to TCGplayer, is currently going for somewhere between $37 and $45 for its non-foil version
The Archmage is an on-battlefield trick, so no one will walk blindly into it, but its also sitting there, preventing them from doing stuff
When you do, add its power to this creatures until end of turn.) Whenever a creature you control attacks, if it enlisted a creature this combat, the creature that attacked gains double strike until end of turn
Yidaro, Wandering Monster As a commander, Yidaro, Wandering Monster isnt as great because you can't cycle it from the command zone, but it's a very neat addition as a part of the deck because it's a free cantrip that cant be countered
I do hope that this series has encouraged you to be curious and adventurous in your deckbuilding