If doing something is described as a piece of cake, it means it is easy to do.
Examples:
Changing the wheel on the car was a piece of cake – I was happy to help!
I don’t know what all the fuss was about – the exam was a piece of cake! I had half an hour to spare.
To put your feet up means to relax, especially by sitting with your feet supported above the ground.
If you gamble on something it means you do something risky in the hope of getting a good result.