Goku’s second son Goten is one of the more difficult characters to use in LSW, because his stats are comparatively low and he does not have much variety moves-wise, as you can see below:
-Kamekameha (beam, 18cc, 25pow, 90acc)
Super Saiyan only:
-S.Kamehameha (beam, 23cc, 30pow, 100acc)
To make things worse, Goten’s only worthwhile attack, S.Kamehameha, can only be used in his Super Saiyan state. If you go with base Goten, your best bet would be to focus on cards with low CC cost such as Energy Wave and Cont.Punch.
Goten has low HP, so upgrading his Life stat at least once is not a bad idea. In battle, there are a number of ways in which you can preserve your health. Using cards like Light Vest and Afterimage will help you avoid enemy attacks, and if you do get hit you can always resort to cards like Dende or Life Preser to get that precious health back.
Just remember that Goten will not last too long, so try to find a good balance between defense and attack. With enough practice you will undoubtedly find a way to use Goten to his full potential.