I also realized that many of the apps available in different sources overlapped, so it became confusing where to get the app from as there would be different versions from different sources.
Eventually, I realized that I only needed a few sources to get the apps I wanted and now I only use about 4 or 5. The other problem about adding sources from some instruction video or site is that it may have pirated apps or can simply have harmful apps. Remember, now that your device can run unsigned code, it can run dangerous code if you alllow it. So you have to be careful about what sources you add. There is a pretty standard list of trusted ones.