To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions (such as Molderhulk's undergrowth ability). The mana value of the spell remains unchanged, no matter what the total cost to cast it was.

Creature cards with other types, such as artifact creature cards, count for undergrowth abilities.

If an effect allows you to cast Molderhulk from your graveyard, its undergrowth ability doesn't count itself. It's already on the stack when you determine the total cost to cast it.

Because tokens aren't cards, they never count for undergrowth abilities.