Would much appreciate an opinion on this deck.
For a start, I go with 24 lands. You're at 15. When everything costs 1 or 2 mana, even then the lowest I've seen is 18 lands. Personally I'd go with 24 lands and never really change that.
You have 14 things that use green, one thing that needs two green, and two green sources of mana.
One thing you can do is count all the colored circles on your cards to find a ratio. Quick count shows you have 28 white dots, 15 green dots, and 4 black dots. Maybe you can do 2 evolving wilds, 2 swamps, 6 forests, 2 golgari guild gates, 2 selesnya guildagtes, and 10 plains.
And on that note, it looks like you don't have any dual lands. It's really hard to play 3 colors, and even harder to play it without the rare dual lands. I would go with two colors. Green white sounds good, since you're only playing with 4 cards using black.
So to tweak your numbers and thinking about your strategy:
White -
Doomed Traveler x 4 (Good 1 mana card, turns into a flyer when it dies)
Concordia Pegasus x 0 (Cut out to make room for ranger's guile. But it's a cheap Flyer, so it's your 2 drop.)
Seller of Songbirds x 4 (3 Drop)
Eyes in the Skies x 4 (Your 4 drop. You want flyers, this makes flyers)
Angelic Benediction x 3
Intangible Virtue x 4 (You have a lot of tokens. This will improve them)
Serra Angel x 1
Pacifism x
Battleflight Eagle x 0 (5 mana for a 2/2 flyer isn't that great)
Sunspire Griffin x 0 (pretty good, but I don't like that WW part of the cost)
Safe Passage x 0
Griffin Protector x 0 (Too expensive for what it does)
Green -
Rancor x 4 (Improves Creature. Great on flyers. Great on your deathtouch creatures. Great Card all around)
Deadly Recluse x 4
Ranger's Guile x 4 (I'm worried about detention sphere and sever the bloodline killing all your spirits. Might replace with Rootborn Defesnes if your place uses supreme verdict more often)
Acidic Slime x 0 (Costs too much, had to make room for ranger's guile)
Fog x 0
Serpent's Gift x 0 (When you use this on your weak creatures, you're basically using 2 cards to kill their 1 card. Not good.)
Prey Upon x 0 (When you use this on your weak creatures, you're basically using 2 cards to kill their 1 card. Not good. This is a great card sometimes, but not for your deck.)
Dual Color -
Selesnya Charm x 4 (Good g/w card. replaces the prey upon for removal, or can save your weak creatuers, or can give you a new creature)
Sluiceway Scorpion (G/Bla) x 0 (Cut Black)
Archon of the Triumvirate (W/Blu) x 0 (Cut Blue)
Black -
Duskmantle Prowler x0 (Cut Black)
Giant Scorpion x0 (Cut Black)
Land -
Plains x 14
Forest x 6
Selesnya Guildgate x 4
Swamps x 0
Transguild Promenade x 0 (Too Slow)
Looking at my own suggestions, I don't have much removal. So that might be a problem