Super Saiyan is the easiest of all to unlock, unsurprisingly. The simple way to do it is to beat the Android Saga as you normally would while doing the story mode for Dragon Ball XenoVerse. Super Saiyan will then be a skill that you can buy at the Skill Shop for 50,000 zeni. You can also opt for the harder but faster way. This has you going through Parallel Quest 14, though. It will be unlocked after the Frieza saga, but keep in mind that Parallel Quest drops are random and this “faster” way may in fact take you awhile.