Though I am a purist, I recommend first watching this movie dubbed in a language that you understand easily:
Since the plot and concepts discussed in this movie are pretty thick, and the subtitles speed by really quickly, you literally will put too much effort in keeping up with the subtitles, missing out on both the great story and animation.
Once you have watched that dubbed version and understood it, watch the original Japanese version in all its glory (subtitles up to you, off course).
Believe me, you will gladly watch it a second time.
