Should I skip B/W and just get B2/W2?
It's up to you! However, Black 2 and White 2's story is based upon the extension of Black and White's story. Ghetsis, N, Bianca and Cheren's storylines also reference back to their Black and White storylines, too - and you will appreciate them more as characters. As well as this, the Unova Link will be able to be used between the two games, allowing you to see a little more into Unova's history. Finally, Team Plasma's storyline also makes more sense as you see Team Plasma's original roots, and why the two sides of Team Plasma oppose each other.
So really, it depends on if you want to see the first storyline, Route 10 (!), whether you want Black 2 and White 2's storyline make a little more sense, a Unova with only Unova Pokemon up until post-game and playing the two games that were rated 40/40 by Famitsu, or if you'd rather save money.
A lot of people here would recommend getting the games, but B2/W2 can still make sense without B/W. If you do choose to get the games though, your experience with Unova will definitely be enhanced and you will likely appreciate B2/W2 more than if you didn't get B/W.