I build a lot of things, mostly mechanical, things I'm to cheap to buy. And being old, and not getting into computers and the net until very late in life I have a hard time with drawing software . but I when working out a design for something resort to CAD, Cardboard Aided Design. I draw stuff to either full size or to scale depending on the size of it. Then with thumbtacks for the rotating points(axles) I can see if the geometry of something will work or not. Saves the money and time of making it in real material and shows where or if there is a problem.
I know you say you don't have many tools, but you do seem to have a few Harbor Freight stores in your area. If Your going to do things that need some precision machining spend a little and get tools, like a drill press or what ever from there. People make fun of their tools but one from HF beats not having one at all, and they aren't all that bad. And just like the big name tools they need to be adjusted to get the most out of them. Stuff right out of the package isn't always ready to run and do the best work.