While Thunderbolt is better than Shock Wave, getting the TM for it would require you to grind in the Game Corner to get it (unless you wait until later, where you'd have so much money that you could just buy it), which if you're willing to grind for a TM, it'd instead be more efficient to grind EXP. Raichu would've had Thunderbolt already at this point too, with the added benefit of it being a more effective Thunderbolt user than Nidoking. Shock Wave can be used temporarily for Nidoking to deal with the early game Flying types, and later should be replaced with Ice Beam or Thunderbolt, as you'd have enough money to purchase it, unless you've spend it all on something else.