Torterra can't learn Magical Leaf, maybe you are thinking of Razor Leaf or Leaf Storm?
Seed Bomb and Wood Hammer are both good moves. SB is power 80, WH is power 120 but has recoil so it's your choice.
Seed Bomb is an egg move so you'd have to breed with a compatible pokemon to get it.
Wood Hammer is a "level 1" move, which means you can learn it by giving a Heart Scale to the Move Relearner in Pastoria City.