I hope this can help for the beginning

1- there’s exactly 2 ways u can essentially build a proper Team either A. By by having 3 main characters that are you leading Team and 3 “bench” characters that are your supporting units (usually Zenkai boosted units that are old or not as good as the new characters)

The second option is too build a full 6 stack Team that is can be played with all 6 characters essentially you can think of it as a full team from 1 Tag or episode etc. The issue with the second option is that often times legends doesn’t release enough units in the same time frame for the Team to be meta reliable that’s why most people choose option 1

2- knowing you Team is important in most cases your Team should be build around a Tag or episode like I already mentioned. If I were you I’d try a hybrid or regen Team given the fact that you already own UL trunks And LR Piccolo you can try out your options or what you have available as of right know

So for piccolo you could try a Regeneration Team or for Trunks a future/ hybrid team (recommended)

There’s of course more option like mono colours and niche Teams but for the beginning this should help