As Neil has said the first thing to do is to decide what you want the machine for & what sort of materials you would like to cut. From that the size, manufacturing materials & electronics can all be worked out. People will keep you straight on what to buy & what not to buy if you ask but obviously it does require some input from yourself.

I doubt having a plotter will be of any benefit to you with something like this unless you want to make it look pretty once it is built

The other thing about having a hand in the design & build of the machine is that when things go wrong at least you have some knowledge already which can help with sorting the problems out.