After coaching a couple guys with chambering, I'd recommend separating the machining processes into three categories. Note: the first two should be practiced on barrel drops or old barrels with the chamber parted off (make sure diameter after removing full chamber is enough to form a shoulder to test fit on an action.
1. Indicating the bore. Until you wrap your head around this completely, it doesn't matter how well you do any of the other machining operations. There are different ways to indicate, I recommend indicating straight from the bore. It'll save you money on range/grizzly rods, bushings, and stacking tolerance errors.
2. Machining and threading the tenon. Turning, facing and threading. Experiment with different tooling, speeds and feeds. Practice until you can produce good surface finish, thread form, and of course accuracy.
3. Chambering. It's time to move to a fresh barrel blank. Fine to pick a less expensive blank but the rationale is you will need to actually shoot your barrel to determine how well you machined the chamber. If you start with a beater barrel, you won't know if it's your chambering work or a worn out barrel. Go slow, measure often, and check your work with a bore scope. Look for clean chamber walls, defined junctions between sections (body, shoulder, neck, freebore and leade/throat). You will no doubt overshoot your desired headspace at some point. Understand and learn how to set back the shoulder and breech face to bring the headspace back to correct depth. Test fire for accuracy and inspect fired brass for signs of grooves or other defects in the chamber.
There is a lot to learn before becoming competent with a lathe, but machining and chambering a barrel is absolutely something that can be self taught. There are quite a few accomplished self taught barrel turners here, ask questions.