If you are tight on a budget try these cool tips. I promise you will have as much fun creating them as enjoying them.
Milk Crate Oasis
Pretty simple put all you need is to milk crates and a steel paint bucket. Pretty cool right?
Party center and Michael will be your friends for this. You can get the sturdy plastic containers from the container store. You can buy 3 inch wood boards, wrap them in fabric and take the grass hut supplies from party city to create a great backyard space your friends will love. You also have a place to store things.
Crate Seat Heaven
The above is cheap and easy. Uline offers wood skids. You can stack them. Treat them and add simple pillows and cushions.
The key thing here is that you can keep the cost down and have a great relaxing oasis.