You hurl an orb of energy at a target within range. Choose Acid, Cold, Fire, Lightning, Poison, or Thunder for the type of orb you create, and then make a ranged spell attack against the target. On a hit, the target takes 3d8 damage of the chosen type.
If you roll the same number on two or more of the d8s, the orb leaps to a different target of your choice within 30 feet of the target. Make an attack roll against the new target, and make a new damage roll. The orb can’t leap again unless you cast the spell with a level 2+ spell slot.
Using a Higher-Level Spell Slot. The damage increases by 1d8 for each spell slot level above 1. The orb can leap a maximum number of times equal to the level of the slot expended, and a creature can be targeted only once by each casting of this spell.
* - (a diamond worth 50+ GP)
One might argue the wording specifically says "...a creature can be targeted only once by each casting of this spell." and interpret that to mean the initially targeted mob upon casting. I'd rule the bounces, if any, can pinball, as long as there's at least two mobs within range to target. Subsequent castings cannot target the same initial mob as a previous casting... Not game-breaking, and keeps the pinball flavor. YMMV