For my performance clutch I use Mobile1 full synthetic 10w30. I have nothing but good things to say about that oil, works wonders. ATF type oil is also good but youll have to change your oil every few rides.
For ultimate protection, power and engine life of a two stroke motor you should use a Castor based oil at 25:1 ratio.
My preferences on oil would be Maxima 927 or Castrol R30, but there are other excellent Castor based oils.
If you are referring to transmission oil then use a good quality oil designed for motorcycles with wet clutches, or Automatic transmission fluid type F.