Here is the full list of all 31 Idle Clans achievements.
Your first level up
Complete the tutorial
Join a clan
Create a clan
Perform a leaderboard search
Achieved upon reaching your first million
Reach a billion gold
Refine an item
Enchant an item
Reach level 100 in a skill
Reach max level in a skill
Receive a boss key
Defeat a boss
Join a minigame
Plunder a small, helpless village
Steal from the royal clan
Prepare a special dish
Eat a burger in battle
The true test for any respectable chef... Make a pizza.
Grow some watermelons
List an item for sale
Send an item to your clan's vault
Defeat a dragon
Create a godlike item
Battle a monster with an Outstanding weapon
Create silver jewellery
Equip diamond jewellery
Smith a piece of Astronomical armour
Purchase an upgrade
Purchase your first property. It's nothing to brag to your parents about, but it's a start.
Purchase the most glamorous property available