Meteor Helmet

Meteor armor exists to make one weapon free to fire. With all three pieces on, the Space Gun draws nothing from your mana pool, which turns a middling early magic weapon into something you can hold the button down on forever. For a pre-Hardmode mage that is the strongest option going, and it holds that spot for the whole stretch between the world evil boss and Skeletron.

The free-cast effect also applies to the Laser Rifle and to both Zapinators, the gray and the orange one. That is what keeps the set alive past its own tier. A Hardmode mage swinging a Zapinator that costs nothing can be worth the armor swap in the right fight. The catch is the defense, which is thin enough that anything landing a hit on you after the Wall of Flesh takes a real bite.

You do not have to wait for a meteorite to fall. Meteorite Bars turn up in the gold chests sitting in the deepest part of the Cavern layer, just above the Underworld, and in the shadow chests down in the Underworld itself. A good chest run can put you in the full set before you have fought the Eater of Worlds or the Brain of Cthulhu at all, which skips a chunk of the intended progression.

Silenced does. Costing no mana is not the same as being exempt from the debuff, so a caster enemy can still take your gun away until it wears off. Keep something non-magical in the hotbar for those few seconds. On the other side, the set makes you immune to the rocks that rain down during a meteor shower, which is a footnote right up until you are caught outside in one.

Moving in the full set leaves fire behind you. Dye applied to each piece tints its own share of the particles, so putting a different dye in each slot blends the trail into a gradient instead of recoloring it flat.