Hello! I've been playing Sona a ton lately because she's in a good spot. I believe her poke is phenomenal if used correctly, her spammable heal makes up for the low base heal, and her ult in pretty amazing

PROS:
Sona's poke is outrageous
Sona scales really well
Sona's heal can really sustain
Her ult wins lane, and games

CONS:
Extremely squishy throughout the game (That's why I flash, ult, and Zhonya's)
Quite Mana hungry without tear
Her speed up in only good late game

Tip 1: At level one if you're going for the poke lane, charge your passive up to two stacks so once your get you lane, you can q and power chord for some annoying poke
Tip 2: When your jungler ganks, it's more helpful to use your E + Powerchord to make a massive slow
Tip 3: If you are in brush and use Q, you won't get revealed
Tip 4: Try to have the Q aura up as often as possible, especially when your carry attempts to harass with a spell like Piltover Peacemaker, so the AD/AP aura will make it deal a little more damage.

In team fights, you want to ult as many people as you can. Flash + Ult + Zhonya's is my way to go in team fights. If you don't have Zhonya's, don't recklessly flash in unless you KNOW you can ult as many as you can. Poke if possible before fights and during fights if you aren't already dead, keep spamming that heal. It could save a life.