Definitely start from DB if possible.
There's always DragonBall Kai if to cut down the number of Z episodes.
Super is probably most accessible (i.e. it's on CrunchyRoll, the POP channel airs it, although they do some weird censoring, and BBC iPlayer. Both of those don't seem to show the Tournament of Power episodes though) and it is watchable without prior knowledge, but I wouldn't recommend starting with it.