When playing Cassiopeia Support, ask your ADC if its OK to get some kills.
You will do a lot of damage after the first recall, most ADCs can not do as much damage as you will do.
So you will get some kills forcedly.

Level 1:
- You are an easy target, don't get caught by CC, stay save and don't force an early all in, you will lose it
- If your ADC wish, you can use you Q on Caster Minions to DOT them a bit for early Level 2 advantage. However, you normally will not have enough Mana to spam your E for a kill
- Use your Q and AA to poke the enemy's to get some gold and reduce there health, wait for enemy's to wast there damage ability before you risk a unhappy trade

Level 2:
- Now you can spam E properly, if a target is low on health, you can try to use your Mana to do some damage, else save it for your level 3 W skill to have an escape
- Don't forget to target the same target as the adc, you still are the support
- Regenerate some Mana by not casting anything to be ready for a level 3 fight

Level 3:
- Now you can "support" your ADC a bit with zoning, use your W to stick an enemy on the ground (no flash, no dash) or to seperate them from each other and have a 2 vs 1 situation. This is based on the enemy's positioning
- At level 3 you will have 150 Mana from Biscits and some Mana from your Manaflow Band, this opens the way to perform a well resourced E spam

After your first Recall:
Buying a Sapphire Crystal will unlock the ability to fight permanently, don't be shy to punish your enemy's with Q+Ex2 when they try to farm, use your extra movement speed to sneak back behind your Minions. If you chose to go all in, be sure that your adc can keep up. Else you risk a 1 vs 2 (and your adc will also die afterwords)

Ultimate Unlocked:
- Use your ultimate mainly to protect your ADC in a all in scenario and to slow a target to secure the kill

You may want to check some questions while playing Cassiopeia Support:
- Do I have to place a ward?
- Can I use a Biscuit / Potion for some Mana / Health?
- Can I poke with my Q safely? (Are the enemy's CC on CD?)
- Do I have to secure the kill or can my ADC do it? (better save then sorry)
- Is there a team-mate nearby or do I solo roam again? (stay with your ADC, he will need your E and R)

Thanks for reading this Off-Meta guide.
Hope you got some inspiration and I wish you god's blessings and peace for your life.