To everyone asking about rerolling, here's my $0.02:
I've played One Piece Treasure Cruise a looooot, and having a strong character, while not vital, really can make a big impact later on. Starting out it's all the same, everyone does well, but later raid bosses and events can be done easier with the right characters. It also depends on how much time you want to put into it, because you can be very unlucky with RNG.
My advice if you have the time is to keep rerolling (the first pull and the second with the 5 stones after the first tutorial, if you want to go that far). If you didn't get a SSR, reroll. [NOTE: To reroll I've had to delete, reinstall, and press "Restart" when prompted]
IF! You find two characters you like, do the transfer device in the options. That way you'll have the code for your favorite team for a while (not sure how long, OPTC is a week). For me, I got lucky. Second reroll was SSR Vegeta and Android 18, good abilities and team so I'm sticking with them.
Personally, I'd say give it maybe 10 tries max. After that, pick you favorite team and get on with the game. They'll be plenty of chances to be screwed by RNG again