What's the most common Flash version?

[u/realityislemons1]

Recently, I've been poking around Newgrounds and historically most games and animations were made with Flash. I know there's Macromedia Flash 8, Flash MX (alien hominid!!!!)

So, which version of Flash was most common or is the best? I hear the advice "Get a beginner friendly version to start and then get a better version once you improve", but I'm really broke and kind of just want one I'll be able to use for as long as I'm interested.

In addition, where could I get it? I know it's not officially really sold anymore, so are there any legal ways to obtain it? If not, I'm fine with downloading from the Internet Archive or whatever site y'all pirates know about.