Let's start with cards I cut or multiplied

2 phantom centaur (becomes 4 Phantom Centaur)

2 hallowed healer (Becomes 0 Hallowed Healer)

2 battlewise aven (becomes 0 Battlewise Aven)

2 phantom flock

1 jasmine seer (becomes 0 Jasmine Seer)

3 seton's desire

2 brawn

3 elephant guide (becomes 4 Elephant Guide)

1 thriss

1 cagemail (becomes 0 Cagemail)

4 giant warthog (becomes 0 Giant Warthog)

1 phantom nantuko

2 second thought (becomes 0 second thought)

1 forcemage/nullmage advocate (becomes 0)

1 chastise (becomes 3 Chastise)

1 wall of spears (becomes 0 Wall of Spears)

1 exoskeletal armor (becomes 0 Exoskeletal Armor)

2 sanctimony (becomes 0 Sanctimony)

2 moment's peace (becomes 3x Moment's peace)

1 patrol hound (becomes 3x Patrol Hound

3 werebear

1 deepwood tantiv (becomes 0 Deepwood Tantiv)

1 rejuvination chamber (becomes 0 rejuvination chamber)

I cut the life-gain and some of what I think of as sub-par cards. Giant Warthog is such a card (the standard 3-mana creature for green is Trained Armadon, which is a 3/3).

The deck looks like this, now:

4x Phantom Centaur

2x Phantom Flock

3x Seton's Desire

2x Brawn

4x Elephant Guide

1x Thriss

1x Phantom Nantuko

3x Chastise

3x Moment's peace

3x Patrol Hound

3x Werebear

That's 29 cards so far. Now, an average deck has about 23 lands and 29 + 23 is 52, so you now have 8 cards to add. I would suggest:

4x Basking Rootwalla

2x Tireless Tribe

2x Serra Angel

the Serra Angels are great flyers, especially with elephant guide on them, and can dominate the board. The Tireless Tribe gets you a way to discard Brawn besides patrol hounds, and can get you threshold. Both the Tribe and Basking Rootwalla can also be played on turn 1, when your deck normally doesn't do anything.

4x Phantom Centaur

2x Phantom Flock

3x Seton's Desire

2x Brawn

4x Elephant Guide

1x Thriss

1x Phantom Nantuko

3x Chastise

3x Moment's peace

3x Patrol Hound

3x Werebear

4x Basking Rootwalla

2x Tireless Tribe

2x Serra Angel

13x Forests

10x Plains

This should make your deck more consistent (especially with the added land and 1 casting cost creatures) and more powerful.