I just picked up Magic again for the first time in 8 years. When I quit playing there were no planeswalkers and a ton of new mechanics, but nothing too weird to learn on the fly. When I last played you would see 1 base set with 2 expansions a year. You also would get a Core Set(8th Edition, Magic 2013) every summer or sometimes a fun set like Finkel Vs Garfield or Unglued.
Standard decks will use cards from last year and this year, and that is when the game gets expensive is when half of your playable cards rotate.
I want to play Standard again but everyone I know who still plays told me to wait until after Return to Ravinca is out and tournament legal to build a deck.
I've been playing EDH Commander for now. Its a goofy format, and the pre-constructed decks are out of print, but its a lot of fun if you can find a way to get started. The store in my town has Commander league every Sunday and people are always in there playing Commander.