A noncreature permanent that turns into a creature is subject to the "summoning sickness" rule: It can only attack, and its {T} abilities can only be activated, if its controller has continuously controlled that permanent since the beginning of their most recent turn.

If a noncreature artifact becomes an artifact creature this way and then another effect animates it, the new effect overrides March of the Machines's effect. For example, Chimeric Staff is a 4/4 creature while March of the Machines is on the battlefield. If you activate Chimeric Staff's ability and choose X = 5, Chimeric Staff will be a 5/5 artifact creature for the rest of the turn.

If a noncreature artifact is also another card type, such as enchantment or land, it will retain those types in addition to being an artifact creature.

If an Equipment becomes a creature, it can no longer equip a creature. If it's currently attached to a creature, it becomes unattached (but remains on the battlefield). You can activate the Equipment's equip ability, but it won't do anything.

Each artifact land has a mana value of 0. March of the Machines makes them 0/0 creatures, which are put into the graveyard as a state-based action.