Cheapest priced copy (The Lost Caverns of Ixalan): $0.35 at Card Kingdom, near mint, their price list as of .
Adaptive Gemguard 
Artifact Creature — Gnome · 3/3 · Common · The Lost Caverns of Ixalan · #3
Tap two untapped artifacts and/or creatures you control: Put a +1/+1 counter on this creature. Activate only as a sorcery.
Legal inCommanderBrawlStandardPioneerModernLegacyVintagePauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The Lost Caverns of Ixalan | 3 | Common | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 10 November 2023You can tap any two untapped artifacts and/or creatures you control, including Adaptive Gemguard itself and other creatures you haven't controlled continuously since the beginning of your most recent turn, to pay the cost of Adaptive Gemguard's activated ability.