I want to get back into Magic (competitively), probably MTG Online, where should I start?

I am so out of the loop, as I always am when I leave/get back in, but I want to get back into Magic. I used to play tournaments locally and was ranked in the top 10 so I was pretty good.. I would like to start on MTGO and practice there because I don't have the time or friend group to playtest locally.. but I'd eventually like to play in some regional tournaments etc.

Anyway, where to start? I was thinking about just going with a popular deck but they always come out with new cards so quickly..