First things first this is my first build. With that being said i have had nothing but success with this build and it is very enjoyable. By the end of game have confidence that Sona will hit HARD!!! With that being said the idea of this build is to maximize the effectiveness of one thing, her passive. Sona's power chord is not something to overlook and with this build the idea is to have it hit harder and faster before you will have any opposition from your opponent. (BTW the potions are there for a just in case and they are cheap)

PROS
Great Support
Can do great burst damage and get out quick
UNDERESTIMATED

CONS
very squishy
team dependent
weak until level 6
might be focused

By the end of this build Sona will have enough attack power to be able to take care of herself. So the thing to focus on is survivability and being able to make use of her abilities.

GHOST- once you have your boots, celerity, and boots you will be able to run so fast almost no one will be able to catch up with you. use this ability to gank or to run away from an unfavorable situation. definitely a must have for Sona.

Ignite- I like this ability for Sona because once i start stacking my items this spell works great for getting assists and kills. So ignite is great.

Sona is a team player. Hence she is a support. Up to level 6 you are going to be fairly squishy and you need to have your team mate. HEAL your team mate when he needs it. The better your team mate the longer you can lane and the more gold you can get. I prefer to got top or bottom with a carry and or bruiser. It is easier to get more kills. When you get you ult USE IT EFFECTIVELY. Shortly after you hit 9 you will be working on mejais and SotO and needing stack. Your Ultimate is awesome at getting kills and assists for your items. Either use your ult for a strategic gank or use it when you know that you are going to get a kill. Either way the ult plays a huge role and can change the tide of any battle. Play defensively early and you can be aggressive later. But i cannot stress enough on how squishy that she is. Just be able to Zone Effectively and last hit like a pro and heal/speed up your team when they need it. Altogether if you can do this you are lined up for great success

Power Chord is Sona's passive and everything in this build is focused around that. Being able to stack mejais and SotO is key to this. Along with Lich Bane you should be hitting champions so hard that they will be fearing Sona. Last Whisper was just an add on and is situational with your game. The games i have had i haven't been able to buy before the opposing team has been defeated or surrenders. I have had nothing but success with this build and build order.

Hope that you will enjoy this build as much as i have and i would like to hear your comments and see some of your scores