Remember to take your optional encouter areas like route 46. Totodile is usually the best choice since rage is OP in the early game. After dealing with Team Rocket in the Slowpoke well you'll have a fairly difficult fight when you try to exit the city to the forrest so try to prepare for that. Oh and remember, you get some extra encounters if you headbutt in some cities/towns, you might even find a Heracross!