Originally Posted by D_E
do i need to collect them to advance in the story or to help me ease some levels or should i just ignore them!?
You don't need them to advance the story. The 30 in each episode gives you the combination to open the episode's safe and get a new technique. I'm on Ep 5 and only opened the first 2. Don't know if the others are useful or not.
You also need to collect 30 clues for the associated trophies.