Watch this instructional poi spinning tutorial video that describes how to start spinning poi isolations. This video is intended for those beginning poi spin isolations, not for those beginning poi. A decent aptitude in poi is recommended, but move-wise, there are no other prerequisites.
This lesson introduces you to the world of isolations and provides an outline of what they are, what they feel like and recommendations on how to start practicing them and developing your own feel for them.
Become confident spinning them like this before you move onto any actual isolated moves. If you can already confidently isolate the poi individually in each hand, then this tutorial isn't for you, and you should move onto an isolated move tutorial.