Early Game Buy left to right. Healing Rite will upgrade into Rescue Beam. Mystic Burst will allow you to deal more damage to the enemy with Splatter (1), and Guardian Ward will allow you to keep your laning partner safe when they go in, or try to get out. Feel free to grab an Extra Starter for either more healing, or more damage.
Extra Starters Pick Restorative Locket if the enemy spam abilities. Healing Nova is more expensive but will allow you to heal multiple people. Extra Regen for more passive regen. Spirit Strike is to deal more damage with Puddle Punch (3).
Mid Game Buy left to right. Use Rescue Beam one someone in The Cube (2) to pull them to you safely! Positioning is key, so always try to remain behind your allies rather than in front of them. Once you get Echo Shard, you'll be able to Double Cube your allies! Don't be afraid to grab another Active from the lists on the right.