I realize this is a month old, but I'll give my thoughts.
Bayleef is the hardest starter to use in GSC. IMO it's pretty much dead weight for the Elite 4. It's doable but your others are going to be doing the heavy lifting. I've used it to take big hits or inflict poison, but it's offense is limited IMO. It does get Body Slam, though I think it's better for paralysis than it's damage considering Meganium's offensive stats & not being a Normal-type.
Furret is solid, if slightly lacking in the Attack stat for the late-game. I've found that Dig & Shadow Ball are excellent for Furret. Allows it to be somewhat of a do-all Pokemon you can send out if you have no other answers.
Wooper's Attack stat & learning Earthquake on it's own are both very good things to have. It's Sp. Atk is good enough to make solid use of Surf. Plus you need HM users, so it works. Only downside is it's low Speed, but that can be mitigated & it has the bulk to take hits anyway.
No experience with Togepi/Togetic, but my brother said it was difficult-ish when he'd use it for runs.
What to look for (IMO):
-Abra/Kadabra or Drowzee/Hypno. Kadabra has more offensive power but Hypno has better defenses. All can learn the elemental punch TMs sold at the Goldenrod Dept. Store, which is a very valuable thing to have. Remember, the punch moves are based off the Sp. Atk stat.
-Anything that can learn Ice-type moves. See the above point. There aren't many Ice-type options until the late-game (after Pryce), so I'm not sure how they'd stack up against the E4 with how stat development works in the older games. Lapras is pretty much the earliest Ice-type. But there are plenty of Pokemon that can learn the Ice Punch TM.
-Mareep/Flaafy/Ampharos. Great bulk for an Electric-type, though slow. Gets good power & status moves. Overall a solid pick.
-Magmar. Fire & Electric moves (Thunder Punch) & good offensive power overall. Somewhat of a glass cannon though. Better defenses than Kadabra but not as good as Hypno, to give you an idea.
-Chinchou/Lanturn. If you decide to not do Wooper/Quagsire, Lanturn is a solid choice IMO. Massive HP, Water and Electric moves, and gets Thunder Wave. It's stats aren't great on paper, but it's better than it looks due to it's massive HP & status moves.
If you're not wanting to put HMs on your main team I have two suggestions:
-Farfetch'd. Caught on the route from Mahogany Town to the Lake of Rage. Can learn Cut & Fly. Farfetch'd is a permanent fixture in all my older Pokemon playthroughs, lol.
-The red Gyarados at the Lake of Rage. Gets Surf, Whirlpool & Waterfall.
