I recommend reusing sod to construct berm and use large pieces of cardboard (Ikea dumpster dive) to edge and mulch sides.
Most important lesson learned, take the Rain Garden 101 class. I gained valuable information and know-how to build a rain garden. Watching my first rain garden at work inspired me to build 3 rain gardens in my yard. They are beautiful and they perform a valuable function in absorbing rain water runoff from the house and garage roofs.
Don’t be too worried about it, have fun, plan it out and enjoy.
Start with a good plan. We took the rain garden class offered and studied magazine articles and searched the web for information for our plan.