I've only come across a few recipes that require a basic armor/weapon to make a better version of that armor/weapon. But I'll share what I've got:

Weapons:

• Swords:
Troika > Khorovod
Cutter > Vile Striker

• Guns:
Voltech Alchemer > Voltech Alchemer MKII

• Bombs:
Haze Bomb > Fiery Vaporizer

Armor:

Jelly Shield > Rock Jelly Shield

( Additionally: has anyone come across the upgrade of the Brandish? I feel that it might be the Cautery Sword, but haven't come across a recipe for it. )