A lot of people think that buying a 3D printer is the answer. It isn’t. Without establishing firstly that you can use a CAD program to design parts, the printer becomes an expensive ornament. There must be thousands of printers out there that are never used because the owners can’t do anything other than download useless things off Thingiverse and print them. The way to go about it is to download a CAD program, Blender/Openscad whatever, then spend a few weeks using You Tube tutorials to learn how to use it. It isn’t an overnight process, it will take dedication, perseverance, and an understanding of the terminology, as well as learning how to create objects that will actually print, how to design them to save filament, structural integrity, faster prints, splitting large objects into smaller ones, interference fitting and so on.
Once you have mastered the CAD program, and allow a couple of months, then look at the printer you need to print the things that you design. The CR10 has a large print bed and a huge following, its smaller brother also. Once you have the printer you can then look at setting it up to print, problem solving etc.
You can test your files using Cura without a printer, the software is all free, and way cheaper than buying a printer and then realising that you have neither the time or aptitude to make use of it.
3D design/printing is not a simple thing, not even remotely simple. Unless you have a lot of spare time and are prepared to lock yourself away night after night to learn, it’s a non-starter. I have been doing it for around 4 years, most days/evenings, and I am still learning.