If an effect refers to a "[subtype] spell" or "[subtype] card," it refers only to a spell or card that has that subtype. For example, March of the Drowned is a card that benefits Pirates and features Pirates in its illustration, but it isn't a Pirate card.

To determine the total cost of a Dinosaur spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions. The mana value of the creature remains unchanged, no matter what the total cost to cast it was.