In Horizon Forbidden West, there are many arrow types, and Aloy needs to craft arrows to use with the bow. Initially, Aloy only has the Hunter Bow and the basic wooden arrows. Use wood ridge to craft the basic arrow. Later when the heroine get to the Forbidden West lands proper, the heroine can get acid arrows.
1 Craft Basic Arrows
The heroine can craft basic arrows. Get ridge wood, and then craft these basic arrows, which are still very useful, and as the ridge wood never runs out, the basic arrows never run out.
2 Craft Acid Arrows
Aloy can craft acid arrows after the first Hunter Bow upgrade at Chainscrape. Aloy will need the acid arrows to defeat the mad bristlebacks with the acid canisters on their backs.
3 Craft Fire Arrows
Unlock the Hunting merchant at Chainscrape and get the Fire Hunter Bow first.