Rarities

There are four different rarities in Crab Champions: Rare, Epic, Legendary and Greed

Rare

Being the most common type of rarity, rare items are the most common items a player will come by and they usually have weaker effects than the higher rarity items (with some exceptions)
Rare items will make up the majority of your inventory, especially in the early game so you shouldn't shy away from them. Later on, many of the rare ugrades can be exchanged tho
There currently are (?) rare items in the game as of V2003, (?) of which are weapon and grenade mods, (?) perks and 10 relics

Less common to come by, epic items usually have a stronger effect than lower rarity items and the right epic item will often help out a lot during a run
Always found in Epic and Spiked Chests, there is also a small chance for epic rarity loot to be found randomly in other chests and totems, as well as a upgrade in an Upgrade Chests
There currently are (?) epic items in the game as of V2003, (?) of which are weapon and grenade mods, (?) perks and 15 relics

Usually the rarest type of loot to come by, the right legendary item can single-handedly be a game changer for your run since their effects and buffs are some of the strongest in the game
Always found in legendary Chests and Totems, there is a very small chance for legendary loot to appear randomly in common types of Chests and totems
There currently are (?) legendary items in the game as of V2003, (?) of which are weapon and grenade mods, (?) perks and 5 relics

Greed perks are quite rare in that they only drop from greed totems, greed chests or can be obtained from the shop
While always having a downside to them, like not being able to drop any greed perk from your inventory, greed perks can often make more than up for it with their strong effects (keep in mind, that there are some greed perks where the effect is almost neglectible in comparison to the big downsides)
There currently are (?) greed perks in the game as of V2003.
The greed rarity is unique in that it only contains perks

The perk Streamer Loot increases your chances of getting higher rarity loot, with the exception of greed perks
Having more goods for sale at the Shop with items like Tony's Amulet and Special Delivery or having more loot choices in Chests with Coral Amulet and Big Chests, you increase your chances of seeing higher rarity loot
The higher the rarity, the better the item. While true for most cases, there are some notable exceptions (like Sharp Shot, Coral Amulet and Ring Of Parrying) and there are also a lot of rare items that have unique effects like Grip Tape or Stamina that you can't find in other upgrades so it is wise to not neglect rare items and upgrades