Gimp is free but not as user friendly as Adobe Photoshop Elements (PSE). PSE is under $100 I believe and touts features in the newest version that are worth not considering the earlier versions.
Photoshop (PS), if you're new to this is not an option for a number of reasons. First, it is pricey; even with a student discout. Second, the learning curve may get you. Getting used to a pen tablet and learning a new application is quite a feat. Third, if you're new to this then you won't make good use of the power of PS. While I want to believe you're looking to buy, I say save your money.
Autodesk Sketchbook Pro (SBP) is strictly drawing. It was designed to handle drawing in ways I don't feel PS does. It is also $100 and Amaon just had a Gold Box sale where it was $60. Look for it on eBay for a slight discount.
In your post you mentioned drawing then said something about photo editing. If you want to draw then SBP is it. If you're editing photos then I recommend PSE. Understand I'm not against Gimp, but I also feel it has a learning curve greater than PSE. Plus, PSE is designed with the casual photog in mind. Download Gimp as it is free. Try it and see. Then consider if you want to draw and edit photos then look into enhancing your collection and stay with Gimp if you love it and add SBP.
I think SBP will also use your tablet in ways other apps may kit. Again, this application is designed with the sketch artist on a pen tablet in mind.
Finally, one last thing to look to is mh Wacom came with some software. It may have been a trial of Corel Draw (another option for you). Look at bundled software as well.
Best of luck.