Depending on the budget, various materials can be used to build your own frame or you can buy a market one. A frame does not need to be only one material. For example, you will notice that many frames consist of a combination of different materials.
Wooden frames are simple, easy to build, and more importantly, you can make any change you may think of, later on. As far as the frame is concerned, the cost of damage after a crash is very low. These are almost all the advantages of a wooden frame. You can either buy some wood and cut it by yourself or give instructions to your local shop about the dimensions. Lastly, when creating a wooden frame, make sure to cut it with a laser; this way you will be able to design it precisely according to your dimensions and hopefully have a stable quadcopter.