When Goten and Trunks perform the Fusion Dance they become not Trunten or Gonks or Troten, but Gotenks! This character has access to the mighty Super Saiyan 3 form and comes up with the strangest moves, including flying flaming donuts and explosive ghost clones. No, I am not kidding.
– Kamehameha (beam, 16cc, 20pow, 100acc)
– S.Kamehameha (beam, 23cc, 30pow, 100acc)
– Galactica D. (beam, 10cc, 15pow, 100acc)
– S.G.K.Atk. (beam, 28cc, 40pow, 80acc)
– V-ball Crash (TEAM ONLY, damage, 33cc, 60pow, 100acc)
– Kiai (item, 8cc, Guard Down, 95acc)
Now don’t be fooled by S.G.K.Atk’s (Super Ghost Kamikaze) immense power of 40 – it’s accuracy is only 80, which is rather low. Opponents will dodge it quite often, and then you’ve lost 28cc for no reason. Instead, a good strategy is to use Galactica Donuts over and over and over. Put it in Gotenks’ limits and you have unlimited use of this low-cc card. If you upgrade Gotenks’ ki stat, the card becomes a strong and reliable weapon. It might even be a good idea to use Kiai alongside it to lower your opponent’s defense, but that is completely up to you.
With that said, if you really prefer to use more powerful cards, I’d recommend S.Kamehameha over S.G.K.Attack.
And then there is V-ball Crash. This card can only be used in Team Battles, but Gotenks’ partner can be anyone (except for Goten, Trunks, or Buu-with-Gotenks-absorbed for obvious reasons). At 33cc it’s not cheap, but it is powerful and fun to use.
DBZ:LSW, your one and only stop for everything to do with Dragonball Z Legendary Super Warriors on the Gameboy Color 
But if you use accuracy hit cards you can use low accuracy powerfull beams like SGKA with no problem, characters like recoome or androids needs those cards to make hits 100% accuracy (recoome ultimate melee 50% acc, android 16 comet punch 30% acc or infernal beam 70% acc