The usefulness of ANP is that you have two options in selecting the gradient.  It would be best to try both a reversed-phase gradient (from 80% to 20% aqueous) and then an ANP gradient (from 20% to 80% aqueous) as an initial screening process.  From the preliminary results you can determine which mode is most likely to produce the best separation.  

Once the direction has been selected, then the gradient can be modified to reach the desired retention and separation of the components in your mixture.