Cheapest priced copy (Modern Horizons): $0.39 at Card Kingdom, near mint, their price list as of .
Fists of Flame 
Instant · Common · Commander Masters · #223
Draw a card. Until end of turn, target creature gains trample and gets +1/+0 for each card you've drawn this turn. (A creature with trample can deal excess combat damage to the player or planeswalker it's attacking.)
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
7 printings · $0.39 to $1.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander Masters | 223 | Common | $0.49 | $0.99 |
| Commander Legends | 414 | Common | $0.49 | — |
| Foundations Jumpstart | 550 | Common | $0.49 | — |
| Modern Horizons | 123 | Common | $0.39 | $1.99 |
| The List | CMR-414 | Common | $0.59 | — |
| The List | MH1-123 | Common | $0.49 | — |
| Avatar: The Last Airbender Eternal | 166 | Common | $0.49 | $0.99 |
3 rulings from Wizards of the Coast
- 14 June 2019The bonus that the target creature receives is locked in as Fists of Flame resolves, counting the card drawn during its first effect. The creature won't get an additional +1/+0 if you draw another card later in the turn.
- 14 June 2019If the target creature is an illegal target by the time Fists of Flame tries to resolve, the spell doesn't resolve. You won't draw a card.
- 14 June 2019If a spell or ability causes you to put cards into your hand without specifically using the word "draw," Fists of Flame's effect doesn't count them.