You need to learn enough to learn what you do not know .
One way to do that is buy one of the minimal , lets say $7 - $20 generators , a kit may be best , so you have part of what may be needed with a general repair / learning bench .
Then you may learn you need something costing $100 or even $3,000 ++ BUT BUY THE CHEAP ONE 1ST
I've been in a number of trades requiring expensive test gear , and found that often learned more / faster [ and having access to the high end test geared , usually in someone else's shop ] that with the new knowledge / experience , that I could do a lot more with minimal test gear .
Then once your in the repair environment , you'l find good deals on good gear , for me finding dead / damaged gear , costs less and then learning to repair just gets me farther down the road .