How do I create my own designs in mambo? Can I do it at all?

Mambo cms is one of the cms which templates are very easy to create. All you need to know is the code for left block, main body, and right column which you can assign by importing the codes in the template.

There is a thing call mambo stand alone service (MSAS) where in you can easily make your mambo template using mambo dreamweaver extension software. Go to mambosolutions.com there you will find step by step guideline on how to create your own template. But you must know how to use dreamweaver at least.