Budget Build using what I had on launch day. 0 Forma Not optimized but it will do the job. Primary goal was efficiency and sustain.

at time of build
1 Yellow Shard for Casting Speed.
1 Red shard for Ability Strength.

Can blast through all of star chart up to level 50 like an absolute breeze.

You regen 2.6 energy/sec
Every ability is cheap. it costs .25 because of the Efficiency to Duration ratio of 175% / 95% so -

Book costs 1.25 energy to summon and .5 energy to cast. it is effectively infinite.

Light and Dark Verse costs 5 energy to cast.

Final Verse costs 12.5 energy to case.

A full buff (6 light verses and 3 Triumph) gets you around 20k Over shield and costs you 67.5 Energy.
A full nuke (2 dark verses and 1 tragedy) that covers most of Helene/Hydron for leveling costs you 22.5 energy.

Perfect starter build for book dps or just endurance sustain. Honestly If you take the yellow shard out and just play at the slower casting speed he has infinite energy because it takes as long to cast as it does to [Regen] the cost but then you have to play according to his casting speed and not take as much risk.

The only other thing to say is if you dont have primed mods, use the not primed ones. results will be slightly weaker/less efficient but it's entirely still viable. Also this build assumes you can farm [Dante]. so youve done the quest to get umbral but regular [Intensify] is absolutely fine. Energy Nex and Fleeting are probably the hardest tog et but i picked mine up completely at random while doing other stuff so it aint impossible.