As others have mentioned, I’d start with a fixed focal length macro. Either one specific to your camera, or something you can get a suitable adapter for. I don’t know what’s what in the Canon world, but Nikon’s 55mm macro, with its 1:1 extension tube works well, and they are available inexpensively, especially the non-“auto indexing” versions. Vivitar and Tamron made some macros too, either would likely be less than Canon’s version.
Another option might be a bellows unit and an enlarger lens.
As mentioned, autofocus is sort of convenient, but is not essential, and often just complicates things.