I think most blues have their own preferences of spell sets, whether it's soloing or for ball builds. For me, I usually do the following.
My Imp solo w/45:
Actinic Burst
Plasma Charge
Disseverment
Frenetic Rip
Zephyr Mantle
Firespit
Head Butt
Bludgeon
Frightful Roar
Refueling
Hysteric Barrage
Magic Fruit
My Cannonball build w/45:
Plasma Charge
Self-Destruct
Fightful Roar
Firespit
Zephr Mantle
Vertical Cleave
Saline Coat
1000 Needles
Bomb Toss
Cannonball
Cocoon
Heat Breath
Pinecone Bomb
Uppercut
I'm pretty sure some of you guys have your own favorite builds. Any other BLUs wanna share theirs?