If you purchase the greenLean, you will get everything you need except a router, computer to operate the machine, and software to control the machine. You state that you have a computer. You can use this computer, but you will need to determine if it has a parallel port, or if you are going to need the USB controller option. As for the software, there are too many different options for you to choose from. We would not be able to tell you which to get, and how much it will cost you. This is a matter of preference. I can tell you, however, that you will need 3 types of software to complete a CNC project. You will need CAD software to design your design, CAM software to add tool paths and convert the design to g-code, and then control software to take the g-code and operate the machine.
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I am a novice to CNC and I am building the "Book Build" CNC machine. I need to know whaqt software I will need to get me started routing simple signs and lettering and maybe some simple stuff