Upload & Sell: On
As a start, I would suggest buying Lightroom 5 (you should be able to get an educational version for less than $100), and learn how to use it by watching the tutorials available on adobe tv or the B&H channel on Youtube.
The video tutorials are a good place to start, but to get proficient with the software you will need to use it for a while.
Lightroom will allow you to do many kinds of image manipulation without needing a pixel editor like Photoshop. Once you are comfortable with everything LR has to offer and understand its limitations, I would suggest buying PS Elements and learning how to use it. PS elements should be sufficient for most of your pixel editing needs, especially if you enhance it with plugins like the NIK Software Suite (you can buy NIK for a little over $100 if you look for a coupon).