Is it better to buy, or mine/gather?
‘gather as you go’ is the rule of thumb, but if you’re at 80, that means back tracking, in which case, you will find that the low levels of crafting may be more time efficient to run events in Orr or do dungeons like CoF and then buy the mats.
If you tend to do things like grind out your daily in Queensdale (for the frequent events.) then mine as you go, and salvage everything that drops along the way.
For weapon smith, you’ll spend a long time needing iron, and quite a bit of it, because Iron will be both your 2nd and 3rd tier raw material (first Iron weapons, then Steel.) My best advice if you want to self source iron is to head for Hrathi Hinterlands and chain centaur events for a while. Same thing as in queensdale, salvage away!
All in all, it comes down to: Would you rather grind gold and buy things, or grind mats? If you buy mats, then you save time which can be spent getting your cash back up to par, or doing other things you find fun.
If you want to self source mats, and don’t yet have 100% map completion, you can get other things done while you farm the mats, and will have more coin in pocket at the end of it (but you will spend more time.)
Does that answer your question?