First time playing Astrologian... need some advice/tips

[StarRosie]

Only advice I can give (Since others have covered the bulk of important tips.) In a pinch, Synastry+Nocturnal Sect+Aspected Helios can provide a good amount of breathing room since the shield blocks an amount of damage equal to 150% of the HP healed when the shield is put in place and Synastry ups your healing potency, so this will result in stronger shields. So if things are going south, hit this combo to cover your party with a good amount of EHP, and it will give you the breathing room to pop lightspeed and SPAM THE DAY LIGHTS OUT OF HELIOS!

Also remember to relax and have fun! A stressed healer can be a sloppy healer.

[Cynfael]

...to pop lightspeed and SPAM THE DAY LIGHTS OUT OF HELIOS!

On a side note to any new ASTs who might not be aware, keep in mind that this isn't literally how Lightspeed works since it does not change your GCD at all, just the casting time.

It's still good for added mobility and MP cost reduction, but the only spells you can spam faster under its influence are those with a cast time greater than your GCD.