I saw your questions last night, and they would've required a lot of time to answer so I ignored them. But I have time now, so here we go. I'll edit this post as I answer each one.
* What should I be investing my stats in? In Souls I would usually specialize in 1 or 2 stats, but in this game it seems like they encourage you to spread out. I've got like ~13 in everything but dexterity and skill, which are both around 6 or 7. But putting extra points in Strength doesn't really seem to do much for my damage, even though I'm using an Axe.
Weapon scaling in this game doesn't work like it does in Souls, where you'd get like +5, +5, +5, then +4, +4, +4 for each point into the relevant stat. You might only be getting 2 points of damage for your NEXT point into strength, but the point after that could give 5. The numbers jump around. You could see boosts like 5, 3, 1, 5, 3, 1 etc with it changing as you put points into the stat. As for your stat spread, don't worry about it. Most people will go 20 points into Dexterity/Magic because there are missions later that have 20 dex/mag as a stat requirement. I played NG and NG+ with a stat spread of 15 body/15 heart/12 stamina/10 strength/as much skill as possible/20 dex/20 mag/25 spirit. I eventually got 99 skill and started branching into body and heart some more.
* Should I be Reforging and Soul Matching frequently? Reforge seems ok, but Soul Match, it's like by the time you find an item with a better level, might as well just equip the new item.
You really shouldn't worry about Soul Matching until you're around level 100, since like you said, you're just constantly gonna be getting better stuff. Thing is, if you find a weapon with perfect attributes, you may not want to let go, and that's when you Soul Match it up to appropriate level. Soul Matching the SAME piece of equipment more than twice makes the cost go up exponentially though (think like, 15+ million gold). I think Team Ninja did this so people wouldn't stick with the same weapon for the entirety of their first run. In NG+ though, green quality (Divine) gear becomes available and those can be soul matched infinitely without the cost going up significantly.
* Are the stances really that important? I've gone through the entire game so far just hitting mostly the strong attack in high stance. Gets kinda boring just seeing the same move over and over but it seems pretty effective.
Yes, stances are important. But you're using axe which I don't know enough about to explain why stances are important, so someone else needs to answer this one.
* Should I be switching up weapons and mastering all different types, or does it not matter?
There's no "should" about this. Do what's fun or you won't have fun. I played 170 hours with nothing but dual katana. Just yesterday started branching into spears.
* Same with Guardian Spirits, can I just pick one and stick with it or should I be varying it up?
I played with Paired Raiken for 170 hours. I switched to Kato this past weekend when I finalized my mixed armor set and weapons. Just go with the one that complements what you're focusing on at the time. Like, there are some guardian spirits that are better for farming rare drops, etc. I'm a damage whore, so I picked Kato for obvious reasons.
* What are the best stats to look for on equipment? Like what would be a "godly roll"?
-Close Combat Damage (the percentage varies. Perfect is 15%, which goes up to 20% with max familiarity).
-Close Combat Ki Damage (percentages vary)
-Guard Ki Reduction (percentages vary)
-Change to Attack <a stat name> A (this adds even more scaling to your weapon based on what stat it is; for example Change to Attack (Strength) A+ would make your axes scale EVEN MORE with strength than they already do, so you start seeing boosts like 7, 5, 3, 7, 5, 3 with each point you put into strength.
-Some people like Close Combat Life Drain. Personally I think it's trash; I don't need to drain shit amounts of health as I attack.
-Final Blow Damage
-Close Combat Ki Usage (percentages vary)
* Do people use all these random drops? I don't think I've ever used a single non-refilling consumable (i.e. elixirs, onmyo magic, ninjutsu don't count). Just fills up in my inventory.
I don't use the majority of the stuff, but there are a lot of useful things in there. Summoner Candles if you die with a ton of amrita stocked up and you don't trust yourself to get back to your grave. Saisetsu-shin sake for amrita farming. Etc, etc. Just read the descriptions. Stuff you throw at enemies, I generally don't use.
Okay, that's it. Phew.
might be harder than anything in Souls. However, level/gear probably plays a stronger factor, so they might be trivial with the proper setup.
