The true ending is fairly easy to get. I thought I'd gotten stuck when in reality I was already 98% of the way there.
Here's what you do:
When you can, explore the different areas during the weekend and just talk to everyone. If you just visit different areas each time and talk to everyone, and accept everything they offer, you'll eventually get everything.
When new rooms open up for you, you'll see sparklies that'll give you an item. Collect all the items from all four areas and you'll get the true ending.
The only real puzzle is near the very end
This'll get you the last three items you need to get the true ending, every other item you should have gotten from looting rooms or just talking to people.
Other than running out of time, there is no way to fail or softlock yourself. So don't worry about making a wrong choice and accept every offer.
If you're struggling with energy or xp, the game also give you a cheat option right from the start.