Nothing much to say, have fun playing Sona Mid :)

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It needs pratice to lasthit but once you can do that all other is no problem.
First always buy Lich Bane and Athenas. You need the Dmg, the Mana-reg and the CDR!
Boots: CDR boots, if you are against Kata or Leblanc buy mres boots! Against Zed, Yasou or Talon you can choose for Ninja Tabi Boots .
After you need Ludens Echo! The passive is a static shiv for Ap!
With your passive + lich bane proc + ludens passive (100%) you can nearly one hit enemys when they aren't stacking mres. Remember: Dont Focus the gank XD

In Lane:
You must work with you passive in lane. Keep always an eye on your passive stacks and use it with your "q" to poke the enemy down. Use you "w" for heal and shield but not so often, you need the mana for the "q" and the pokes! If you are under attack or a gank is cooming use your "e" and move under you tower fast! And dont forget to farm!
After first back buy always 2 wards to ward both sides of the mid lane against the enemy jungler. Lee Sin or other fast ganks can hurt a lot so take care and ward! ALWAYS! Even in late game buy some wards and replace ward trinket against Oracles Lens to control the enemys vision!

Have fun !