Collectables and both types of scrip are fundamental systems for endgame gathering. If you're wondering where the level 90 legendary nodes are, you have to turn in enough white scrip collectables to purchase the book for each node (3 for MIN, 3 for BTN, 3 for FSH). Each book requires 16 "C" tokens, and each token costs 100 white scrips. So you'll need to farm 1600 white scrips for each book. Once you purchase a book it'll open up the legendary node but you'll either need to look up when and where it pops or find it on your own. The mats gathered from these nodes will be required to craft the new gear coming out with Savage. Otherwise you can gather the sub-90 mats and sell those on the marketplace, but a reminder that mats from here on out (until 7.0) will be locked behind the collectable and scrip systems.