Given the old iOS version supported by the first iPod, it's difficult to find working version of the apps. You can try, however, to download old, compatible versions. In order to do so you need a PC/Mac with iTunes: once in the iTunes's App Store section, just download any app that you need, to make them appear in your purchased list; then search for the same app on the device, and if there's an old compatible version, you should be prompted to download that. I advise you to try with free apps, at least at first, or with apps that have been around for a long time (they most likely were running on that device)