1. Level Up Croconaw: Ensure that your Croconaw is at a high level compared to your rival's Pokemon. Train Croconaw by battling wild Pokemon or trainers on Route 32 and Route 33.
2. Teach Croconaw Strong Water Moves: Croconaw learns powerful water-type moves as it levels up, like Water Pulse and Hydro Pump. Teach these moves to Croconaw to exploit the weakness of your rival's Pokemon, many of whom are Grass or Fire-type.
3. Use Status Effects: Consider using status-inducing moves like Toxic, Sleep Powder, or Paralyze to weaken your rival's Pokemon and make them easier to defeat.
4. Type Advantages: Your rival will have a Quilava and a Zubat. Quilava is weak to Water-type attacks, while Zubat is weak to Rock-type attacks. Use Croconaw's Water moves against Quilava and switch to a Pokemon with Rock-type moves (such as Geodude) to deal with Zubat.
5. Recover Croconaw's Health: Keep an eye on Croconaw's HP and use Potions or Super Potions to restore its health if needed.
6. Consider Your Team: In addition to Croconaw, have a balanced team with different Pokemon types to cover various weaknesses. This will help you counter your rival's team more effectively.
Remember that battles in Pokemon Gold can be challenging, and sometimes it may come down to luck. Be patient, keep training your Pokemon, and adjust your strategy as needed to secure victory against your rival.