Like INFERNO was just saying, Photoshop ain't free - I was reading a review only yesterday with the subhead,
Why does the upcoming Adobe Photoshop CS5 cost $600?
GIMP on the other hand is free. And it'll do everything you need it to - virtually none of the high-end Ps features are anything you'd need to even touch for mini photos.
Now on to this part of your original question:
What's the easiest way to make your mini look good with a solid background, etc...
Take a good photo to begin with.
If you get together a good setup for indoor photography and practice a bit nearly every photo will be decent or better, which will greatly cut down on the amount of post-processing that you need to do.
If you take a good shot just a bit of Levels and
maybe one or two other tweaks should be it - that's 30 seconds to a couple of minutes tops per image with practice, versus tweaking something back and forth for half an hour trying to get the colour right if it's got a bad cast from the lighting and/or any reflected light from a coloured surface nearby.
Einion