Gathering gear, you have no choice at all. The item for any given slot is either Crafted, and has no bought equivalent, or it is bought, and has no crafted equivalent.

Unfortunately, you can use your Gathering Scrips to buy gear, or to buy Favors - but due to the number of scrips you need per piece of gear, and the weekly cap on obtaining them, you cannot effectively do both. That means you cannot make your Crafter gear, either, on those weeks you are saving for or buying Gathering gear.

This system is worse than that 300 Mythology cap way back when.