Omnath, Locus of Mana

You don't lose unspent green mana as steps and phases end.
Omnath, Locus of Mana gets +1/+1 for each unspent green mana you have.

Timbermaw Larva

Whenever Timbermaw Larva attacks, it gets +1/+1 until end of turn for each Forest you control.

Target creature gets +1/+1 until end of turn for each Forest you control.

Create a 1/1 green Insect creature token for each Forest you control. Shuffle Beacon of Creation into its owner's library.

Enchant creature
Enchanted creature gets +1/+1 for each Forest you control.

Create a 2/2 green Wolf creature token for each Forest you control.