Healing is pretty easy in this game. Here's a rule of thumb: If your gear is golded out, you're spamming orbs/shards, heals, ele drain, and people are still dying, it's not your fault, they just have a cp or positioning problem. You want to be behind everyone so they can be in range of your heals while being close enough to keep an eye on the tanks. You're gonna want to farm Spell Power Cure, Olorime's, Jorvuld's, Mending, Infallible Aether, and Sanctuary. In dungeons I weave crushing shock to help with damage, but in trials you want to focus on heals and keeping ele drain up. And since you're a templar, keep channeled focus up 100% of the time because it gives you a lot of tankiness and magicka regen. Everything else is just presonal preference.

Orbs ele drain and combat prayer those are the most important skills I feel like. Of course healing springs as main group heal and breath of life for an "oh ***" heal other than that, getting the right gear etc comes later. I am not a healer don't know all the things they are doing but dps players will love you for ele drain and the tank will love your shards and the whole group needs orbs