Cast an Elf from your hand by paying its mana cost.
If the Elf was green, Nettle Sentinel triggers, untapping itself.
When the Elf enters the battlefield, Cloudstone Curio triggers.
Holding priority, activate Heritage Druid by tapping it, Nettle Sentinel and another Elf, adding {G}{G}{G}.
Resolve the Cloudstone Curio trigger, returning Heritage Druid from the battlefield to your hand. 
Cast Heritage Druid by paying {G}.
Nettle Sentinel triggers, untapping itself.
When Heritage Druid enters the battlefield, Cloudstone Curio triggers, returning the Elf cast in step 1 from the battlefield to your hand.
Repeat.

Infinite LTB

Infinite ETB

Infinite storm count

Infinite green mana

Heritage Druid

Nettle Sentinel

Cloudstone Curio

Cast Banishing Knack by paying {U}, targeting Nettle Sentinel.
Cast the green creature card from your hand by paying its mana cost.
Nettle Sentinel triggers, untapping itself.
Activate Earthcraft by tapping the green creature, untapping a basic Forest you control.
Activate the Forest by tapping it, adding {G}.
Activate Nettle Sentinel by tapping it, returning the green creature from the battlefield to your hand.
Repeat from step 2.

Combos with "Nettle Sentinel"