If a planeswalker you control is also a creature (most likely because it's Gideon), it will be counted twice as Ajani's first ability resolves.

The tokens created by Ajani's second ability are similar to the card Ajani's Pridemate, but they have no mana cost and their mana value is 0.

If Ajani's Pridemate is dealt lethal damage at the same time that you gain life, it won't receive a counter from its ability in time to save it.

The ability of Ajani's Pridemate triggers just once for each life-gaining event, whether it's 1 life from Impassioned Orator or 4 life from Dawning Angel. If you gain an amount of life "for each" of something or "equal to the number" of something, that life is gained as one event and the ability of Ajani's Pridemate triggers only once.

Each creature with lifelink dealing combat damage causes a separate life-gaining event. For example, if two creatures you control with lifelink deal combat damage at the same time, Ajani's Pridemate's ability will trigger twice. However, if a single creature you control with lifelink deals combat damage to multiple creatures, players, and/or planeswalkers at the same time (perhaps because it has trample or was blocked by more than one creature), the ability will trigger only once.

Whether you have at least 15 life more than your starting life total is determined as Ajani's last ability resolves.

In a Two-Headed Giant game, life gained by your teammate won't cause Ajani's Pridemate's ability to trigger, even though it will cause your team's life total to increase.

In a Two-Headed Giant game, Ajani's last ability exiles permanents as long as your team's life total is greater than your team's starting life total by 15 or more life.