Honestly most softwares are good enough if your design is good enough. Ideally an Adobe Suite is in order, but if you got the flair for it and the control for it, unless you have unusual graphics, most programs can hold out for you. If its good enough for someone to see the potential, they might be willing to revamp it for you.
I personally do everything by hand. No borrowed flourish vectors. Nothing clip art. They restrict and control your design so you have to "live with" what you can find. Everything I've done is by hand from pencil, to pen, to digital pen in illustrator. That's then taken to photoshop. I'm not saying you need to pay a bajillion dollars for a software program. I'm saying if your focus isn't on your initial design, hiding behind software programs won't help.
The great thing about a regular pen/pencil is that you can sketch ANYWHERE, ANYTIME! Who needs an iPad.
-Chin