I bought a fairly simple printer (TEVO Tarantrula) from AliExpress some time ago, it had some issues, but after a bit of patience and googling I have a device I'm quite happy with. As it came as a kit, I had to put it all together, and the devices themselves are really uncomplicated. Of course people far more talented than myself had already done all the hard work in terms of software, my unit uses "Marlin Firmware" (
http://marlinfw.org/) which gets dumped on a Arduino based board and bobs your uncle. And after watching a few youtube videos, some of which were from this guy, (
http://www.makersmuse.com/) I'm fairly comfortable with the whole thing.
In terms of CAD software, I use Fusion360 (
https://www.autodesk.com/products/fusion-360/overview) it has a 30 day fee trial which can be made unlimited if you register as a hobbyist/enthusiast, it is an Autodesk product like TinkerCAD, but significantly more powerful, in my humble opinion.
If 3D design is not your bag, then (
https://www.thingiverse.com/) has all sorts of objects you can just download, send to your slicing* program directly and print.*Slicing programs are what takes your CAD designed masterpiece and chops it up into little layers that your 3D printing software can understand, i.e. boatloads of X,Y,Z co-ordinates.
3 major slicing programs I've come across are;
CURA (
https://ultimaker.com/en/products/cura-software) which is free
SLIC3R (
http://slic3r.org/download) which is also free, but was last updated in 2015, and we are still waiting for the April 2017 update
SIMPLFY3d (
https://www.simplify3d.com/) which is less free at $150