Try to get sighstone after your first back. After that if the enemy team is ap heavy go for locket as it is literally one of the best support items in the game. If the enemy team does not have a lot of AP then go for Righteous Glory for engage!
i always rush sighstone and then go straight into a Catalyst Aeon. the new passive is sick on him (also stacks on the champions passive). but the top three items on him are Righteous Glory, Frozen Heart, and Locket of the Iron Solari, if you can get all 3 of these items completed there should be no fathomable way for you to die in a fight.
Feel free to pm me any questions :)