Bore sizes vary.
Some people need to use smaller than .440 with their guns due to the small bore size.
If components are harder to come by locally, I would buy .440 roundballs and then buy .012", .015", and a pack of .018" patches. If you need larger ball, the thicker patch makes up for it.
Lube is a whole another story. As many recipes and preferences as there are shooters.
Olive oil, beeswax, Crisco, wonderlube, and many others.
I like pre-lubed patches, just easier to use. I use the CVA yellow pre-lubed ones. My patch goes in a bit tighter. However, I fin d the bit tighter patches keep the bore cleaner.
Back to ball size. It seems some manufactuers back in the 70 and 80's had more varying bore sizes. Seems the guns made in the past 20 years are much more likely to handle a 440 ball with a .015" patch. This is a generalization of course.