I got on that $12 deal from BB for 2.0 starter pack with Stitch and Merida. I bought 3.0 digitally and have the Empire pack. Is there any reason to ever play 2.0 again? Unless I get the Marvel level packs that were made for 2.0?
I picked up 2.0 after 3.0 and I think that the level packs are the only reason to go back to 2.0. You can unlock items for the Toy Box mode with 2.0 characters in 3.0 by just scanning the figures. You can't play the 2.0 Play Sets in 3.0, only 2.0.
So I know absolutely nothing about Disney Infinity.
What would I need to start with? Can I just buy playset 3? would I need the originals? is it possible to just go digital?
Only interested in the star wars content
It's best to get a starter pack at first because you'll need an Infinity board to scan the figures to unlock content. This will give you the board, the Twilight of the Republic Play Set (which is my favourite so far) and a copy of the game. You can go digital as the game is on each consoles web store but you'd still have the disc version if you buy the starter pack, though you can trade it in.
If you'd prefer to go digital, you could buy the Infinity board separately, as the PS3, PS4 and Wii U ones are all compatible with each other, and then pick up the Play Set that you like and the game. Xbox One and Xbox 360 Infinity boards will only work with their own console i.e. a 360 board won't work on anything but a 360. There's no difference between the Infinity board that comes with 1.0, 2.0 or 3.0
If you're playing on PC, you can just get the Play Sets because you unlock content with the web codes that come with each Play Set or figure. I'm playing on PC so, if you have any spare web codes, I'll be sure to give them a good home
If by originals you mean Infinity 1.0 and 2.0, no you don't need them. The 1.0 and 2.0 games are the only place to play the 1.0 and 2.0 Play Sets but the characters cross over and can all be used in 3.0. You can also unlock items for the Toy Box mode in 3.0 by scanning 1.0 or 2.0 figures but you can play all of 3.0 with just 3.0 characters so you should be set with just the 3.0 starter pack, Play Sets and figures..