You need four-leaf clovers to play at the House of Luck. You can win Township Cash, coins, construction materials, tools, and other useful things there.
Please note: you can only get Drills, Electric Saws, and Jackhammers at the Tool Exchange when you trade in construction materials.
Stocking up on four-leaf clovers is simple:
1. Help your friends and other players load their trains or fill crates in their airplane cargo holds when asked. They send you a thank you letter with a four-leaf clover inside once they accept your help. The letters get delivered to the mailbox at the Town Hall, and you'll know they've arrived when you see an enveloped-shaped icon above the Town Hall.
2. Enter the game regularly to receive daily bonuses. When you log in more than five days in a row, you have a chance at winning a four-leaf clover every day after that.
3. Exchange gifts with friends. Some gifts contain four-leaf clovers.
4. You can always buy four-leaf clovers with Township Cash.