[Xacual]

At chapter 4 you have little need for money, though most money comes from farming materials and selling items much more than anything else. Around chapter 7 or 8 you should be able to drop 100k plus of items into your shop pretty easily. But yeah there are guides up if you google them for areas to run for certain items that make good profit. One example is the naqua ninja blades, another is the barrel pile once you have 66 tools in your workshop though that takes a while.

You definitely want to get Emelita soul shield 3 as soon as possible. I think the earliest armor that has that is the sage armor. You'll also want to upgrade Yuela's fire armor for prevail 3. Serawi, fire armor again, go down the right path for her 9 range nuke and a very strong 3 range one. But for the most part you don't need that many armor upgrades though you're in Eme's route which is considered the hardest on first playthrough so definitely spend some money on Wil's and Eme's.