Sounds like you're doing great! Very cool that you're planning your first 5k.
It took me a long time to learn to judge my pace without checking my phone. (I used the Runkeeper app to track my runs when I did C25K.) A great website for finding music that works with your pace is jog.fm. If you go to this link: jog.fm/workout-songs
you can input your desired pace per mile, and it will give you songs with bpm in that range. You can narrow the search by genre to find stuff you'll like.
As for running shoes, even though you're on a budget, this isn't the place to cut corners. Your shoes can make the difference between having an awesome run or ending up injured. I agree with those who suggest going to a running store and getting fitted. I do think that, as Zorbs said, you should get your first pair at the store that took the time to fit you. (I've never been to a running store that charged for fitting; if yours does, I guess I wouldn't feel badly just doing the fitting there and buying online, but if it's just part of the service they provide--which has been the case in all the ones I've been to--it doesn't seem fair to let them to all that effort and then not give them the sale.) Oh, and you might not know the difference now with your shoes, but when you get the right pair, you'll know! :)