I was successful in most of the games (except for the logic one, for which i seem to be too slow), but I never managed to convince a group. I won several (5-10) times in the category the group seemed to like but still had almost no progress. Maybe I was just too impatient.
Guess the lack UI is more important than i thought then
When choosing a minigame make sure you hold down to fill up the bar at the bottom, it is the required percentage of completion to win points, but it also makes you win that much point. It's like placing a bet on how successful you will be at the minigame.
It is done so that with the right minigame if you bet 100% and achieve that you will make half of the progress directly