Togekiss is a strange Pokemon. It has very nice tanky stats as well as great special attack. The thing is, its speed leaves more to be desired (edit), and is its main weakness. Togekiss can nine times out of ten survive a supereffective attack from a UU tier Pokemon at full health. And this is why many people who use Togekiss tend to get Thunderwave on it. This allows you to slow down the enemy so you will be attacking first, add that to the effect on air slash, and your ability serene grace, you can prevent them from attacking at all, because there is a 60% chance they will flinch and a 25% chance they will be paralyzed. This is my suggestion to you.
Aura Sphere/ Hyper Voice (Good coverage or strong STAB attack)
Airslash (The core of your move set)
Thunder Wave (The other major part of your moveset)
Roost/Aura Sphere/Hyper Voice/HP Ice (Roost is a great move for sustaining your health, however if you do get it, it will allow the enemy a 75% chance to attack (assuming theyre paralyzed) which you dont really want. This should only be used for a tankier build. Then the other moves are just for more coverage)
Make sure you hold leftovers, the sustain will help because you will get free health each turn as they are unable to move.