Hello everyone! I'm new to this challenge (and the forums) so I decided to give it a try with my Sapphire version. The rules I chose are: unlimited Pokémon Center use, allowed items, no repeats, no legendaries, no gift Pokémon, and switch.
After receiving Greg, the Treecko, the first wild Pokémon I met was a female Zigzagoon I named Meg. I was leveling her up in Route 104 when suddenly Youngster Billy sent his Taillow to kill her. I ran to the Pokémon Center, but it was too late for Meg. I was left with Greg and Marla, a Lotad I found in Route 102. However, as soon as I entered Petalburg Woods a wild Shroomish came to join the team. James and Greg fought against the trainers and Pokémon in the woods. They also helped me beat Roxanne, which was a piece of cake with James' Mega Drain and Greg's Absorb. Now I'm heading to Route 116, where I met Ted, the Whismur. I'll train Ted before battling Team Aqua in the Rusturf Tunnel.
Team:

Greg
♂ Lv. 15

James
♂ Lv. 16

Marla
♀ Lv. 4

Ted
♂ Lv. 6
Memorial:

Meg
♀ Lv. 8