You don't need to understand DNA or the Masterclass - you just need to follow the instructions, which are simple and straightforward.I need to go through your works about DNA as it is all above my head.
Since you have tested with Ancestry there is no need to spend any time at other sites, certainly for the first few months after you start following the instructions in the Masterclass. You might find the odd clue at MyHeritage but there will so my more clues at Ancestry that you're better spending your time there.
.You will need some sort of Ancestry subscription, but there is probably little point buying the Pro Tools add-on for the first couple of months, as you'll have quite enough to do without it.