I get past the 4th area, kind of easily, but the 5th and the final boss is cancer. Guides recommend getting a +6 plate armor. How the fuck do I get through the game if I don’t find it. What if I find it in the second or third area? There are not nearly enough scrolls of upgrade to get that high.
What am I supposed to do? I am missing something but I don’t know what.
Specifically addressing your questions on upgrades, since that’s what you asked about; here are lots of tips and tricks, but it sounds like you’ve found a guide that should have many of those. Sorry if you know some of these tips - just laying a few things out there.
There are 15 scrolls of upgrade in the game, three per area. IMO, scale armor can be fine for a win, particularly if you find it already upgraded. As a quick check to see if unidentified equipment is upgraded, I like to throw it on explosive traps - if it’s upgraded, it won’t be destroyed; if it is destroyed, you haven’t lost much.
While I prefer to save most of my SoU for my end gear, it’s not totally necessary. If you’re using warrior, you can put an upgrade immediately on armor with the seal on it - you’ll keep that upgrade through the game, which can be a great help in the early game. Ditto for mage staff - give it at least upgrade early, but it’s totally viable to put more to it if you can’t find a good weapon early.
If you’re feeling frustrated, there’s no shame in taking a break for a while - many players (myself included) take >100 runs before their first win.