whatever your manual sais for oil type. It dosent make an extreme difference . I usualy buy normal oil and change about half way through the year depending on the riding amount. Just check and see with the pull out bolt to see if its milky looking every time you ride.
If you do a search under transmission fluid you will find this topic has been debated here many times and you will see al the pro's and con's on regular motor oil, ATF, and specific tranny oil (there is a lot of topics on this).
That will allow you to decide on your choice. Any will work, some better than the others.