I hoped that someone who plays the JP version would come around eventually and share their wisdom but apparently that won't happen. Which is a bit of a shame, because I'm kinda at a loss what should I do. As in...
1) Up till now I've had one fix team that I've been using since the very beginning. I got lucky and pulled 4 3-star and 1 2-star units from the five tickets I got after the tutorial part. I throw the 3-star units in the party along with Yuuri and presto, team's complete. So my team looks like this: Yuuri (water), Eddie (light), Berta (light), Alena (light), Bianca (fire). I kinda had to realise in the second chapter that this won't work. A full electric team for example wrecks me quite hard. So I guess I should make subsequent teams against specific elements, but I don't even have enoguh units for that, not to mention the immense time investment need to get that done...
2) When is it optimal to use awakening? I mean I don't get too many copies of the same high quality unit, so awakening a skill and then getting stuck with something that might actually worse than the base skill can ruin an otherwise strong character, so I'm very reluctant to take that risk. I did awaken Yuuri's first skill and I got a tier 3 single target skill that can put an enemy to sleep, which is better I guess. But how much better? Should I reroll it? Should I keep it? I have no information on the available skills, so I have no way to rate the relative value of one particular skill. I guess in general it's a good idea to switch out low tier, single target skills, as they will be utterly useless somewhere down the line, but beyond that, I have no clue. Yes, the skill has  number for it's power, but I have no clue what that number is based on. Thus "skill power = 30" is about as meaningful as "potato tastiness = 24". 
3) What to grind? I have no idea which level drops what. As others have pointed out, some maps just don't seem to drop the girls. (Magma Vulcano) Without having any info on the drop rates or at least on the types of loot itself, I don't really know what to grind. 
Basically my main problem is that the game is clearly set up in a way to make the players do some long term strategic decisions on their team, except that the game fails to provide enough information to make said decisions. So whatever I do, it kinda feels like taking a shot in the dark.