Not Updated For Current Season
This is a guild for owning mid to low level players and teams that I have found very effective. Generally speaking Sona has great poke and provides excellent fun for players who want to win without focusing too much on micro plays. A solid base with Sona can carry nearly any ****py team.
Breakdown of Gameplay
I've seen where other guides go into multiple item builds and if then that scenarios, and it's a bit much for the entry level players, and anyone who is experienced probably doesn't need that much of a breakdown so I'm going to step you through how pretty much every game goes and my reasoning for each choice I make on the build I stick to.
First I select Teleport and Flash. Keep an open mind. Buy a Spellthief's Edge, Faerie Charm, and Warding Totem. Put a level into Valor. While still by the shop cast charge once. If your jungler is going to need your help keep it that way, if not charge it twice. When you help your jungle cast valor again to hit the creeps and auto attack and go to your lane. If you didn't help you've already cast twice already. In lane your job is going to be to collect gold and harass. The reason you charge valor in base is so that you can immediately cast on heroes in range in laning phase and start with a triple charged blast to the face. I typically aim for the support unless they are tank based. This hits hard and sets up a psychological advantage. Be aware that you will never be more vulnerable than at level one. I have learned the hard way that you MUST be cautious at level 1. After that feel free to poke away. A second note, don't get grabbed! You can survive almost everything except a well executed grab. As soon as you have the gold to upgrade to frostfang dump all of you mana and return to base. Buy Frostfang and anything else you can afford. Ideally boots, but I never stay that long. I'd pick up another faerie or a potion and teleport back immediately. This seems silly but chances are you won't use the teleport before it recharges anyways and the difference between 15g per hit and 8g in the early game is extreme. Per shot you make up the difference in gold in about 50 shots with the per second gold generation. This is about the difference in time between when you backed and when you normally would, except now you have more mana regen, CDR, and damage. It's a wash for the gold but if you can get the second Faerie charm it's worth it.
Mid Laning Phase
This is pretty rote. At some point you will want to return for a fast sightstone and boots. Ideally, I would buy the boots and a chalice if I had bought the faeire earlier and I had the scratch. Sona is a mana hog so spamming and mana regen are key. I also don't mind getting the quick sightstone depending on how I feel as Sona is very squishy and it beefs her up just enough. From there I'll go into Athenes and then Rylais as the slow is excellent. I've been considering Mikhails recently as well as Eye of the Watcher, but spooky ghosts are just too strong if you use them effectively right now. I've also toyed with a Rylai's Liandry combo for the doubled effect against really tanky teams. It works well enough.
General Skill Usage Strategy
I've detailed pretty much everything in other sections but I can describe how some basic interactions occur. You get grabbed, you die. That's number one. In a team fight, they target you first and you in the mid to back line. Rengar jumps on you perhaps. Ult them, use heal if there are more than one, otherwise use speed move away and rely on your team to target them while they are ulted. Chances are they will as it will prob be their AD carry and your team loves targeting heroes hit by your ult.
Second, your team sucks and can't engage. Speed them up to move in quickly, or wait for them to group in a line, which they will because this is silver, flash in and ult them. Then move away using celerity to return to your team and speed them to the stunned heroes followed by perseverence to shield your team as they follow up.
As you are siege-ing I typically switch between speed to pers to dmg to pers. I bash on Valor but it does provide extra dmg per hit to everyone in radius, which can be quite effective. Do avoid grouping to closely and people will want your auras, but grouping is bad. I use speed to move through everyone quickly and then pers. They don't need to stay in your aura to keep the shield, which is also a major benefit.
Arguments for Windspeakers and Maxing Song of Celerity
This is really the purpose of this guide. I disagree with the highest rated 6.3 guide right now, which has you maxing valor and putting your points into Thunderlords Decree. Thunderlords is great, it does area damage and you don't have to aim! How cool! This is actually my main argument for spellthief VS coin, it's a no brainer. That being said you only have 3 options to hit people and one of them is your ultimate, so thunderlords really doesn't come into play that often. If you're auto attacking someone twice and not using your ult then you're already to close and the cooldown on Valor is too long to allow constant spamming. The truth is you are a support, not a damage dealer. It's better to keep the mana cost of Valor down in order to spam gain money and provide support for your team. I can't tell you how many times I've been in a game where top dies four or five time laning and we still win the team fighting phase. Think about this. How many heroes have a heal AND a shield... especially on other characters? Janna? Possibly with her ult but f that. You get a 10% bonus to heal two teammates AND a subsequent 10% bonus to the shield you then provide EVERYONE IN YOUR AURA. that's ******ed. That's a Locket of the Iron Solari every. few. seconds. Her sustain in a teamfight is nuts and she can interrupt burst chains on over-extended noobs with her ultimate. And oh yeah, runic armor makes heals and shields on yourself more powerful and you happen to have BOTH.
Song of Celerity over valor? I didn't capitalize the second one on purpose. Celerity gives you SO much speed early on and it only builds into the mid game. Every Sona I play against goes Valor and I win every time. It allows me to escape ganks, disengage faster, and engage faster for ganks. It also slows enemies who try to escape. Let's put it this way, you won't outrun a Yii, but if Gragas is chasing you, or someone with better boots you get away whereas you wouldn't have before. Celerity saves lives, and you're a support. You aren't there to do damage, you're there to increase the damage of your team during their boost with valor, heal and shield as often as possible. And speed during engage and disengage when the other team over extends or is on the run. Speed is also great because it allows you to get into and out of their jungle quickly to stealthily place wards.
This is also why my build looks so jenky, but works so well. The key needs for this hero are CDR for faster casting, mana regen, and AP to increase heals, shields, and movement speed buff. Athene's is an item that was pretty much built for Sona. Beyond those key traits I focus on survive-ability, because as soon as the team realizes I'm the reason their *** is getting beat they target me immediately. I ult them and they get blown up then I cast movement to back away and heal back up to return full force. Rylais, due to the nature of Valor as works great. I only change up my build if they are 100% AP or AD. Additionally, the last two item slots are up to you. Banner is great if they are split pushing you. You can swap down to buff the unit with celerity. The extra team resist is also nice. Zeke's can be nice for the armor and zz'rot is a lot of fun with great defense stats.
Alright, I've made my appeal as to why I think the current highest rated build is wrong, or at least why this build is more effective at lower levels. I hope you find insight into Sona play and hey, I may be completely off base, but I win a lot of games with this build and I hope it works for you too. Cheers.