The thing I've noticed about AI3 is that nearly all the decks are very heavy on controlling the field, especially the Gravity/Earthquake Stoneskin elder (oh, how I hate him!)
The thing your deck lacks is staying power... maybe make this more of a Duo, and stick in 4-5 Air Pillars to keep your Pegasuses always Diving, and stick in a couple of Owl's Eyes if you have them. Another option is Sanctuary... if you're running Light, why not take advantage of the poor man's Shard of Gratitude?
You can also use Dragonflies for your Quantum generation... it's a 1|1 creature. Since you're already vulnerable to Creature Control, a few more creatures aren't going to hurt. But, mainly, an air Duo is going to give you access to Sky Blitz and Wings (only airborne creatures hit you).
I love Light, but it's shields are extremely situational and kind of sucky in a mono deck except that Solar Shield is decent. Hope needs Light-generating creatures and Reflective shield is only good against Unstable Gas or Firebolt decks.
If you're going Mono Light, Light has some of the best unupped Dragons in the game, Golden Dragons. They're amazing and have 10 HP so they're not glass cannons that are going to die at the first Shockwave or Lightning Bolt. There's worst things you could do than adding a few of more of those to your deck.
But right now you have 3 Blessings that you're only going to use on Pegasus. Anyway, check this out:
http://elementswiki.co.cc/basics/building-your-first-deck/#lightAnyway, I hope that helped a little. Good luck!
