I dont know if someone has sugested you or not but i Will say that tryout corel DRAW, it really worth the price, few designers over here would really understand why i am saying so..
Well frankly speaking u need to know Photoshop compulsarily if u r entering into any media related field, cuz it makes ur life a hell of a lot simpler, be it web design, 3d design or just illustrations... Not kowing photoshop is like jumpin into the media ocean with an oar in ur hand, but no boat.
You can try getting a student discount on Photoshop. It's best to jump in with the big guns - you will be more productive in it.
Hello, Image Editing : I usually use paintshop pro for most image editing needs, if your budget permits i recommend Photoshop its the industry standard Image Conversion/batch processing : i use irfanview which is free does lots of work including image optimization for web( quality adjustment) sooner or later you will need it, its also a perfect image viewer that is free Free Photoplus : if you need an easy to use free application try photoplus. I haven't tried it but heard good things about it. First being very easy to use. Free GIMP : if you can spend sometime in this software it will be worth it. most Linux guys use this along with blender for advanced 3d animation, visual effects. In short it feature rich.