Cheapest priced copy (Dominaria United): $0.35 at Card Kingdom, near mint, their price list as of .
Gaea's Might 
Instant · Common · Planeshift · #81
Domain — Target creature gets +1/+1 until end of turn for each basic land type among lands you control.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dominaria United | 164 | Common | $0.35 | $0.49 |
| Planeshift | 81 | Common | $0.35 | $0.49 |
4 rulings from Wizards of the Coast
- 18 June 2021Domain abilities count the number of basic land types among lands you control, not how many lands you control or how many of any type.
- 18 June 2021The basic land types are Plains, Island, Swamp, Mountain, and Forest. Land types other than basic land types (such as Desert) don't contribute to domain abilities.
- 9 September 2022The basic land types are Plains, Island, Swamp, Mountain, and Forest. Land types other than basic land types (such as Desert) don't contribute to domain abilities.
- 9 September 2022Domain abilities count the number of basic land types among lands you control, not how many lands you control or how many of any type.