Cheapest priced copy (Double Masters 2022): $0.35 at Card Kingdom, near mint, their price list as of .
Jeskai Elder 
Creature — Human Monk · 1/2 · Uncommon · Duel Decks: Speed vs. Cunning · #46
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever this creature deals combat damage to a player, you may draw a card. If you do, discard a card.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
4 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Double Masters 2022 | 53 | Common | $0.35 | $0.49 |
| Duel Decks: Speed vs. Cunning | 46 | Uncommon | $0.35 | — |
| Khans of Tarkir | 43 | Uncommon | $0.35 | $0.49 |
| Core Set 2021 | 53 | Uncommon | $0.35 | $0.49 |
4 rulings from Wizards of the Coast
- 20 September 2014Prowess goes on the stack on top of the spell that caused it to trigger. It will resolve before that spell.
- 20 September 2014Any spell you cast that doesn't have the type creature will cause prowess to trigger. If a spell has multiple types, and one of those types is creature (such as an artifact creature), casting it won't cause prowess to trigger. Playing a land also won't cause prowess to trigger.
- 20 September 2014Once it triggers, prowess isn't connected to the spell that caused it to trigger. If that spell is countered, prowess will still resolve.
- 23 June 2020You draw a card and discard a card all while Jeskai Elder's ability is resolving. Nothing can happen between the two, and no player may choose to take actions.