Hoard All the Materia
Speaking of Chadley, he’ll be one of your best sources of Materia early on in Final Fantasy 7 Remake. Again, after you unlock side quests in the Sector 7 slums, be sure to speak with Chadley to start taking on his Battle Intel quests. These quests are mostly pretty simple things, requiring you to assess enemies in combat, hit weaknesses, or Stagger them a certain number of times.
For each Battle Intel quest you finish, Chadley will develop a new piece of Materia that you can buy at a discount. Most of his Materia orbs are unique, and can improve your dodge and ATB efficiency.
Aside from that, you can also buy Materia from item shops and vending machines. Similar to the original 1997 game, characters can only use spells and abilities if they have the associated Materia equipped. Because of that, you might want to consider purchasing two of the same Materia. Most orbs can be found in the open world, but if you have the Gil to spare, it can be a good idea to buy an extra at the shops.
This way, you can ensure that you have multiple characters with some spell overlaps, which can be helpful for keeping your party, or hitting an enemy’s weakness quickly. A quick pro tip: Thunder and Fire should cover most enemy weaknesses throughout the course of your playthrough, so keep those handy.
