buu is the strongest to start off with, but he isn't going to stay the most powerful
cause once u transform, that's it. u stay transformed.
so i wish u luck.
for a noob, choose goku or vegeta.
they are the easiest to get familiar with.
then try gohan and frieza [frieza = cheap]
then try krillin and piccolo [hard to control at times.] [also have noob weapons 'disc' 'eyelaser']
then trunks. dont even want to talk about him. [has basically nothing lol]
^_^
hope that helps, cause in my opinion, that is the way i list them.
peace