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I just wanted some clarification here, but is an ability to convert into a creature (from a land or an artifact) regarded the same as a casting "creature spell" (as an instant I guess) in terms of "color creature spells you cast cost 1 less to cast"?

Does that makes sense?

If I wanted to convert a land into a 3/3 creature would an artifact with this ability allow me cast that conversion (as a creature spell) for less mana?

No, you said it yourself: it's an ability, which is different from a spell. If you get a discount on creature spells, it won't affect abilities.

111. Spells

111.1. A spell is a card on the stack. As the first step of being cast (see rule 601, "Casting Spells"), the card becomes a spell and is moved to the top of the stack from the zone it was in, which is usually its owner's hand. (See rule 405, "Stack.")

112. Abilities

112.1a An ability can be a characteristic an object has that lets it affect the game. An object's abilities are defined by its rules text or by the effect that created it. Abilities can also be granted to objects by rules or effects. (Effects that grant abilities usually use the words "has," "have," "gains," or "gain.") Abilities generate effects. (See rule 609, "Effects.")

...

112.1c An ability can be an activated or triggered ability on the stack. This kind of ability is an object. (See section 6, "Spells, Abilities, and Effects.")

602. Activating Activated Abilities

602.1. Activated abilities have a cost and an effect. They are written as "[Cost]: [Effect.] [Activation instructions (if any).]"

Even if it were a spell and not an ability, a creature spell is a spell of type creature, not any spell that causes a creature to be on the battlefield. So, for instance, Resurrection is a sorcery, Animate Land is an instant, and Aquatic Incursion is an enchantment. None of these are creature spells, even though they cause there to be creatures on the battlefield.

If you're talking casting a spell with Awaken, like Ruinous Path then this is an alternate cost for a spell but it still is a non-creature spell, so it could have the cost to cast reduced by things like Jet Medallion but it won't be reduced by Bontu's Monument. Other spells will also animate lands, like Life and Limb this too can be reduced in cost by Emerald Medallion but not by Rhonas's Monument. Wall of Resurgence is the only thing close to a creature spell that will turn a land into a creature, because it turns a land into a creature when it enters the battlefield.

If it's an activated ability of some creature that will animate the land, like Clan Guildmage's ability, there are cards that can reduce the cost, like Heartstone and Training Grounds.

If it's an ability of the land itself, then there is nothing I know of that reduces the cost of a land's activated ability.

None of these are casting a creature spell, only the first is a spell at all but those are instants or sorceries.