I highly recommend that you don’t try cutting out the subject and pasting it on a better background. (Unless you just want to do it for Photoshop practice…) For starters, it’s nearly impossible to get another background that will “match” well enough to look natural without some serious fiddling with colors, tints, and levels. It’s a whole lot of work for not much gain, unless there’s a specific reason you need to do that for a certain photo.
Here’s what I would suggest: Take your camera, grab a kitty, and go find a background that is nice. Take some time to make kitty comfortable, don’t just plop her down and watch her run away. 🙂 Check out this post we put together a while back with some tips for pet photography: https://www.lenspiration.com/forums/topic/tips-for-puppy-photography/
Patience is the key. There are lots of times where I get only 1 or 2 photos out of 100-200 that really strike me as “good”. When you see that one special photo out of the whole bunch, and compare it to your photoshopped-in-background photo, you’ll appreciate the extra work it took to get the “real” one a little better. 🙂