Welcome to the Sona community here on mobafire! just a few tips for your build, it is more effective if you max one ability first, something like q>w>q>e>q>r>q>w>q. This allows for you to have one ability at the max rank at level 9, and one at level 13. Also, for your itemization, Archangel's Staff/ Seraph's Embrace is probably not one of the best items for her, due to the fact that her mana does not really need the buff late game, and the shield from it is not going to be that large with the items in your build. Sorcerer's Shoes are decent on her, but Ionian Boots of Lucidity or Mobility Boots are a better option.

Hope this helps,

~moon