Cheapest priced copy (Battlebond): $0.35 at Card Kingdom, near mint, their price list as of .
Lead by Example 
Instant · Common · Oath of the Gatewatch · #134
Support 2. (Put a +1/+1 counter on each of up to two target creatures.)
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
3 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Battlebond | 205 | Common | $0.35 | $0.49 |
| Oath of the Gatewatch | 134 | Common | $0.35 | $0.49 |
| The List | BBD-205 | Common | $0.35 | — |
3 rulings from Wizards of the Coast
- 22 January 2016You can’t put more than one +1/+1 counter on any one target using the support action.
- 22 January 2016If a spell with support has other abilities that target creatures, those abilities and the support ability can target the same creature.
- 22 January 2016Support can target a creature you don’t control.