Best photoshop software?

I recently got my first dslr camera nikon d5100 btw. But what's a good photoshop software?

LOL "photoshop software". Photoshop is Photoshop, not some broad category. That's like asking "what is the best Burger King restaurant?"
And Photoshop is probably the best. Or GIMP.

If your goal is to shoot using your fine Camera, then Adobe Lightroom 4 is what shooters use.

If your goal is to be a retoucher, then Adobe Photoshop CS6, Extended would be the best