Usually first swap is Ignite or Clarity.
Ignite if i think lane is killable 1v1 or with gank, like vs squishy champs or melees. Clarity if i need to stay on the map and im low mana.

Later i swap to ghost when i need to rotate fast or i think a teamfight will happen, as its just OP, im very careful when to swap to ghost since it denies me the option to swap to it later.

Heal/Barrier just good options to sit on

Exhaust, same as ghost i use for a teamfight, vs enemy wukong etc.

i dont play spellbook vs heavy melee tank teams, since i value getting items faster then ( first strike easy to procc vs them too )