She's a decent support during early game but I disfavor her mid-late game. Her abilities just doesn't cut it and the only useful thing I like about her is her ultimate. I've played a few games with sona either on my team or their team, and the team consisting of sona usually loses :/

Your build seems decent, but I suggest more or at least one more item(s) that passively supports the team.

Sorry for no itens moment.

Tomorrow, a guide! :)