Which audio filter can apply to all of my audio clips to get them to the same level so it doesnt get louder or more quiet from clip to clip?
There is no filter that one can just apply and the audio automagically adjusts, so adjusting on a clip per clip basis on on the timeline is the best way to deal with clips with different audio levels.
Then, go to Windows > Audio Mixer. There you can add a compressor such as the Multiband Compressor or Dynamics. A bit compicated if you are new to audio but it can even out the audio a bit. But it will never be an easy way without adjusting the clips on the timeline.
There are tutorials on the YouTube that deals with how-to-audio in Premiere Pro.
There are new tools for automagically leveling all your clips. You can find great info on the web. Here's a few:
Hope these help