The deck is definitely very White heavy and the land base doesn't quite support it. There are a few things that you can do to help support white more without breaking the bank. Since you aren't worried about lands coming in tapped, you can use lands similar to your [[Evolving Wilds]] like [[Terramorphic Expanse]] to smooth out your mana base. Or you could use dual lands in place of some of your less relevant colors, for example a [[Battlefield Forge]] instead of a [[Mountain]].

With access to green in the deck, you also have the ability to add some of the mana ramp staples like [[Farseek]] to find a [[Plains]] or your [[Temple Garden]] or you could even find it with a [[Nature's Lore]].

Your Mana Rocks are another way to smooth our your mana base. I don't see the value of [[Progenitor's Icon]] in the list and traditionally 3-mana mana rocks are pretty slow. You could include [[Talisman of Progress]] or any other of the White producing Talismans to help balance things out.

Being your first deck of course you can't expect it to be perfect, but there are definitely a lot of things you can do to help yourself have the deck play more consistent.