Early Potions: Varies
TM01: Slot 7 (watch out for slot 6 Escape Rope)
Rare Candy (early): Slot 5 (watch out for slot 6 Escape Rope)
TM11: Slot 6 (new exp. route), slot 7 (old exp. route)
Escape Rope: Slot 5
TM28 (early): Slot 6 (new), slot 7 (old)

Antidote
Potion
Poke Ball
Helix Fossil
(Rare Candy)
S.S. Ticket
TM28