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