It's a pretty good first try, but there lots of things that need improvement.
1. you aren't running quite enough lands in this deck, 24 is a good number, I often do 25 though.
2. You will hardly ever get
Pristine Skywise out, because you only have 3 blue mana sources, you can take him out.
3 There's some pretty horrible life gain cards in this deck, 5 mana to gain probably 5 life is a pretty bad deal, in fact, straight out life gain is pretty bad, take them out as they have no synergy with the rest of your deck.
4. Auras are pretty bad. Most of the time, you would be better off with other creatures anyways. one reason for this is because you can get 2 for one easily. Say, you enchant a
sentinel spider with
hero's resolve, then your opponent casts say, a
doom blade on it. You are down two cards and a lot of tempo. Which reminds me:
5. You need more removal. To me, it is pretty important to have about 4-5 pieces of creature removal and maybe a bit of enchantment and artifact removal in your sideboard. Which brings me to:
6. You can't really just put a whole color in your sideboard. It may look cool, like "so you beat my green white deck, now why don't you try to beat my green red deck?" in reality, that doesn't really work, especially not with only three red mana sources total, main deck and sideboard. Even if you put mountains in your sideboard, it will probably just lead to some
mana screw.
This may seem like a lot of negative criticism, but in reality you could have done a lot worse. (only five mana guys for example). Don't worry, with a little bit of tweaking, this deck can become a real force to be reckoned with!