Wind of Music level 10: This is going to be your protective skill, it's going to be good both for you and your party and it helps increasing the serene gauge a bit
Stigma level 10: Huge damage over time when you unlock the last tripod, if you're playing in a group you can switch to increase serenade gauge by 200%, it increases decently fast for you to heal people
Sound Holic level 10: Same reasoning from Stigma, it can cause huge damage over time, or you can choose to increase serenade gauge by 200%, stigma and sound holic together is enough to fill somewhat 70% of a whole bar
Sound Wave Vibration: Another amazing skill that causes good damage, CC and you can also buff your and your party's attack by 40% while using it.
Optional skills (you can play around with what you think it's best with the remaining points)
Sound shock level 7: This is going to be your filler skill, gives a decent amount of damage for the short cooldown, you can choose to give your party members a boost on their damage or increase your own and wider area of damage
Dissonance level 7: This skill has a low cooldown and decreases the attack of the target monster that can stack up to 65%, I prefer to use this skill to fill up the serenade gauge over time than using heavenly performance that has a much higher cooldown time and I don't find that the skill is worth putting all the tripods for a few seconds of 8% more attack speed
Indomitable Performance level 10: needless to say, it is an amazing support skill, if you want to tend more to the support side, this is a must.