For the Gym Leader's Team, I would suggest something like this:
Normal Type Mons (or mons who were Normal Type in previous stages)
-Marill
Its part Fairy Type helps against Fighting Types, has priority and powerful moves like Play Rough, Superpower (Brick Break better, maybe) and can run coverage moves like Dig or Bounce.
-Fletchinder
Also helps against Fighting Types, and also being part Fire means trouble to all those Bug and Grass mons we encounter early. It also has enough support movepool with Taunt, WoW, Tailwind, etc., recovery in Roost, access to U-Turn and other good moves to be a nice option. Its Ability could even be Flame Body, considering he is pretty fast himself and can run Flame Charge, too.
-Bunnelby
A pure Normal Type-version of Marill, with similar moves and same ability, as it could run almost the same set (Quick Attack, Brick Break, Dig/EQ, Bounce, etc.) ...or he could be the lead with Spikes, Rock Slide/Rock Tomb, U-Turn or even Wild Charge.
-Porygon
The team's main special attacker. Has access to a good STAB move in Tri-Attack and the Bolt-Beam combo (or if that is too much, Electroweb-Icy Wind to give also some support and help its poor speed). Can also run T-Wave and Recover (or Pain Split).
-Chansey
Could be the signature mon, as even without EV investment it has very good special bulk at these levels. Having access to reliable recovery with Wish and Softboiled, I think giving it an Eviolite could be a little overkill, even more if it ends up knowing Aromatherapy or Heal Bell. Everyone knows the extense movepool the Blobs have, so it could be a full-support mon with Toxic/T-Wave or just a semi-special attacker with recovery (maybe giving it Ice Beam + Thunderbolt too, or whatever).
And the non-Normal Type to give more support:
-Gastly
Great defensive typing and help against Fighting Types too and other common types like Grass, Bug, Normal, etc. in this stage of the game, but also frail to not suppose too much of a problem to beat. Good offense and speed and access to Taunt, Curse, Confuse Ray, Destiny Bond, Clear Smog, Hypnosis, WoW, Perish Song...