Fortune's End is both your initiating ability on foes (due to its immobilization) as well as a way to purge Purifying Flame's heal on enemies.
[Purifying Flames + Purifying Flames + Fortune's End (no channeling)] - Consecutive damage before purging the heal with Fortune's End.
Fortune's End cannot be disjointed by enemies. It dispels certain disables so cast this on allies as well if necessary.
[Fate's Edict] - Use it to disable an enemy's physical attack. Also good to block an enemy's spell on a fleeing ally.
[Fate's Edict + Purifying Flames + Purifying Flames] - This will let you heal your ally without them taking any initial damage.
Purifying Flames is your bread and butter! Purifying Flames works in combination with Fortune's End.
For enemies, spam Purifying Flames to then follow-up with Fortune's End to purge the heal. String as many as you can before purging as your range is very good for Fortune's End.
Use False Promise either just as a fight starts or to save an ally. Remember: all heals double after False Promise. So use all your abilities/items that can heal your invulnerable target as soon as possible! This ability is incredibly powerful when used right and taken advantage.
False Promise Invisibility : Your ally is invisible under False Promise's duration.
core items (Safe Lane) 2
Aether Lens to allow Oracle to both save allies or impede enemies with his Fortune's End or Fate's Edict makes Aether Lens incredibly valuable at any point of the game. All of Oracle's abilities work with Aether Lens, increasing their range.
Glimmer Cape can work in conjunction with your ultimate or in your own defense; the situation is varied but given Oracle's Versatility, it can work in a varied ways.
Ghost Scepter in combination with your Fate's Edict, let's you essentially be invulnerable while casting spells.
Depending if you're leading the charge (get Ghost Scepter) or in the back assisting, Ghost Scepter may situationally be proved useful.
Solar Crest is an overall decent item on Oracle who excels in his traditional attacks, but can also use this item to work alongside a full-channeled Fortune's End or Fate's Edict; making the enemy disabled or immobile and taking large amounts of damage thanks to the armour reduction.
For magic-intensive enemy teams, Pipe of Insight can be considered.
Force Staff is due to the situation of Oracle. You want to neither be in the front of fights, but you also want to be near or around to pop your heals, channel abilities, etc. Exchange Eul's Scepter of Divinity for Force Staff if you get caught out a lot or the team is a very mobile one.
Eul's Scepter of Divinity makes that floating sluggish Oracle into a slightly faster slug. The main interest of Eul's Scepter is its purge:
Offensive Combo: [Purifying Flames + Fortune's End (no channeling) + Purifying Flames + Eul's + Purifying Flames + Fortune's End (no channeling).
Spirit Vessel is a great end-game item versus especially tanky heroes or those with a lot of health.
If Aghanim's Scepter, Oracle can heighten his healing abilities as your Purifying Flames stack. Use it with your ultimate: False Promise, or against enemies to nuke them down and then nullify the healing aspect with Fortune's End.