My 5k idiocy

There are times, when I start to question my own sanity.  Lately, that has been my experience.
I recently got the brilliant (i.e. ludicrous) idea to sign myself up for a 5k race. 
I have never even ran a mile in my entire life...let alone 3. I am very inactive and despite being able to walk 3 miles (which I do about 3 or 4 times a week and is my only real form of exercise for the past oh, I'd say 10 years) I cannot run, if my life depended on it. Regardless, that did not seem to stop me from this idea of signing up for this race.
I at least had the decency to sign up for one that is not until September so that I can actually attempt to train for it with ample time. My current standing is that I can run .4 of a mile. And by run, I do not mean actually run of course. I am speaking on my pathetic attempt at a jog. Even still, I am at .4 of a mile. A 5k equals out to be 3.1 miles so I have my work cut out for me.
I've started a workout called "3 weeks to 30 minute running". I am currently on day 3 of it and already my knees are absolutely killing me, full on aching in my joints throughout the day. I know one thing is for sure, I am in dire need of some new running shoes.
What I'm currently working with (hence, the knee issues):

I need to figure out another option, that is not these. What I really need is something that is going to give support and cushion so I'm not getting the horrible knee pain and preferably do away with my shin splints, although I think that last part is wishful thinking. The other problem I'm having is how expensive running shoes are, good ones anyway. Spending $60+ on shoes is out of the question for my budget.
I'm such a cheap skate anyway, I usually only shop at Ross and never spend more than about $20 on any given pair of shoes, so my mind set on costs is that of a grouchy old penny pincher. I even looked at my faithful Ross store today, but I just don't think I will find a real, quality pair there. Also... I really want something wild and fun to motivate me on this crazy journey of attempting this 5k.
I realize it is not the color or style of the shoe, but the comfort and support it provides. I just feel like I'd be way more jazzed about self-inducing punishment of running if I were rockin something like this:

But alas, items such as these little gems would cost me well over $100 which is way out of this broke-living-off-student-loan's budget. A girl can dream though, right?

I have a mid term tomorrow that I really should be studying for. So why is it I'm instead writing about running shoes? Exactly. Procrastination at its finest.