For starters, don the Black Trunks Saga Mastery and get the Trunks Saga Version of Trunks (level 1 and 2) and the Cell Saga level 3 (maybe 4). Now when you start combat, use trunks' level 1 power with your mastery). With Trunks' strong power levels you would probably would have more base damage (maybe 2 or 3).
For more damage, add Black Bearhug Drill (+2), King Kai's Thoughts(+3), and Black Striking Drill (+2)! With those drills/ non-combat cards, you add 7 power stages! I did this once striking my opponent for 11 stages and 1 life card! If only he was at Zero!!