Neoverse

Just to note here, this doesn't include the stages that need the cube as gear. You just have to finish the first 15 stages using Naya as your character.

Naya is probably the most difficult character to play, as Claire can tank the hits and then regenerate with the Vampiric State buff (or God's Answer cards) and Helena can turn into a fortress with the Griffin, or shred her enemies using the Lion. Naya has no such luck. Any of the decks will work, especially at Transcended Universe 0, though in my opinion, the Hybrid and Shoot decks are superior to Radioactivity. Naya also has mechanic called Overheat, where more powerful cards will add to a stack, and every 5 will add an Overload card to your hand. These cards cost nothing to remove, but will deal 3HP of damage if you do. This isn'r really anything to worry about, so I won't mention it again (at low difficulty levels I have never needed to care about it).

Focus your efforts into dealing heavy damage, without using a lot of Mana. Skills that grant extra Force (each point of Force adds one damage per Attack for every card in a turn, decreasing by one each time. Cards like Automatic Shot have this applied per bullet, so receive much greater benefits.) and Mana should be prioritized (more Mana means more cards per turn). Skills that let you receive benefits from being overheated or for playing cards are also excellent choices. I would recommend picking up the following cards if you see them (Evolution Details only given where it makes a discernible change to how the card behaves):

Constants (Yellow):
Infinite Magazine(Evolved) - This card will add a free 0 Mana Shoot card per turn while you have the buff (Evolved ups the damage of the card from 3 to 4).

Scope Attached(Evolved) - Raises the damage of every Shooting card by 1 point. Cards like Automatic Shot receive this per attack, so get extra benefits. (Evolving this card gives it the Promise Attribute, which means it will always be drawn on turn 1.)

Smoke Bomb - A single turn "Constant" that lets you take half damage from all incoming attacks for only 1 Mana. Useful if you need it, but won't always be available. 1 use per battle.

Charging - +3 Mana for next turn. Useful if you don't have anything better to do.

Instants (Purple):
Supply Magazines - 0 cost Instant that functions the same as Infinite Magazine, only it's not every turn.

Time Acceleration - +3 Mana Now, -2 Mana Next turn. Useful for if you absolutely have to make a kill this round.

Attacks (Red):
Slash - 0 cost Attack, deal 3 damage and gain one point of Overheat.
Sharp Blade - 0 cost Attack, deal 5 damage, but only once per battle, as it has the Consume tag.
Radioactive Dumping - 6 Piercing Damage (Ignores Enemy Armour), 2 Radioactivity, for 2 Mana. Not exceptional, but useful.
Aimed Shot - 3 Damage, +1 Mana next turn. Stackable. Very powerful.
Russian Roulette - 2x3 Damage, Lowers Cost by 1 for every Shooting card played this round. Synergizes well with a deck with a high amount of other Shooting cards.
Psycopath - 3 Damage and 3 Radioactivity to all enemies, for just 1 Mana. Very useful.
Radioactive Blow - 1 Damage, 1 Radioactivity for 0 Mana.
Energy Steal - 7 Damage. +3 Mana if the target has any Radioactivity. This one is only useful if you have other cards that have inflict Radioactivity, as it is not worth the 3 Mana cost otherwise (but is effectively 0 cost if the target has any).
Rapid Shot - 3x2 Damage to all, 1 Mana. Very efficent for clearing large groups, and sold against single targets.
Jab Jab - 1x2 Damage, but adds 2 points of Force, all for 0 Mana.

Defends (Blue):
Radioactive Magazine - 4 Armour, every shooting card adds 1 Radioactivity to all enemies for this turn. If played as the first card, can add a solid chunk to damage output for a turn, pairing very well with Infinite Magazine, Supply Magazines and decks heavy with Shooting based attacks.
Accelerated Defence - 8 Armour for 2 Mana. Nothing special, just equivalent to 2 evolved Defend cards in one.
Steroid - 3 Armour for 0 Mana. Free Armour is never a bad thing.
Enhanced Magazine - 3 Armour and gain a Shoot card . This protects you and hurts the enemy, all for 1 Mana. Evolving it isn't really worth it, as the Shoot card just gets +1 damage, there are better choices.
Quick Evasion - 6 Armour. Another nothing special, just a solid choice.