Note: This guide is a work in progress and a basic general guide to playing Wo Long.
I'll avoid spoilers and the more advanced stuff in this guide given the current state of the game.

Is this Game for you?
Do you like Sekiro?
Then by all means, give this game a try through the demo, or spend <2 hours before the refund expiration period.
Koei-Tecmo's Team Ninja isn't exactly renown for storytelling and combat game play is the meat of their games.
Inventory Management / QoL (Quality of Life), UI/UX is quite bad in this game and I will not cover it here - there are many mixed reviews that covers those issues.

Let's get this out of the way - persistence, good reflexes, good rote memory, and a fluid, stable running system is required for this game.

You, the player
Take some time and evaluate your reflexes; the average person's eye can see about minascule changes that happen over 50ms - 100ms.
The average person takes 200ms - 300ms to respond accordingly.
If you're lucky and have reflexes to respond < 200ms, this game will be a piece of cake to you.
Blocking is... valid and forgiving - but do not rely on it since spirit does not regenerate from blocking.
This is important because there are enemies who have chain attacks that cannot be interrupted aside from parrying repeatedly in a timely manner.

Your Machine
There are some goofy things I've noticed in my hours where my inputs aren't seemingly registered despite clicking on before the big red attacks touch me. This could be a combination of inputs not registering OR frame-locked inputs (meaning if a game stutters or suddenly speeds up, enemies can move faster and/or slower given the number of frames - this can completely ruin parry timings). That being said, this a NOT a guide for troubleshooting.
Disclosure: I am a KBM guy, so this may or may not apply to controller-based players.

The Parry System
This game is ALL about the parrying. If you can't parry or don't enjoy parrying-based game play, you can stop here.

There are no animation cancelling and attack commands are queued; meaning if you spam attack, your inputs will follow through and take a very hard one if an enemy lands a hit on you*.
Enemies DO NOT parry your attacks - but other players can and will parry if you have invasion on.

*Normal small and/or human-sized enemies are typically staggered on hit, but they can also spontaneously enter a red attack state, making them immune to interruption unless out of spirit; I've died quite a few times in those instances.

What can be parried? Everything! (If you can nail the timing down) There are already videos online showcasing no-hits and only moving to bait attacks.

At it's core, this game is closer to a QTE (Quick Time Event) simulator than anything else*.

*I am serious here, since QTE in the past were all pressing 1 button to resolve game events and in this game, pressing 1 button for that dopamine hit is very close).

As a player who makes mistakes often enough, this game is very brutal. The best and only thing that can be done is mitigate the cost of such mistakes.

The Stats
Focus on Earth early.
Earth increases your gear weight capacity - meaning heavier armors for more damage reduction.
Earth offers bonuses on deflection, and access to spells that reduces damage taken.
The less damage you take, the more opportunities you have at surviving and winning.

You have your choice of Fire, Metal, Water, and Wood elements;

Fire will improve damage dealing potential.
Metal will improve spell efficiency.
Wood will improve your HP and reduce spirit loss.
Water will improve deflection efficiency; there are also some potential here for elemental reactions from what I can tell, but I am not experimenting yet...

Personally, I went with a Earth and Metal focus to slow enemies down and reduce damage. It should be obvious, but make adjustments as you see fit to your style of play.

Equipment - Weapons
Your weapon of choice early on should be the "Podao"; the closest equivalent of a glaive in the western world. Alternatively the spears are also OK (but I hated them).

Podao damage scales with Earth and Metal and the attack animation speed is OK - but definitely do not use it offensively against faster attacking enemies (such as dual-wielding assassins). The reach is better than swords but shorter than spears. The attacks are mostly swings so it covers a wider area if you are being attacked by multiple enemies*. This is a great weapon for multiple dogs/wolves or small stun-able targets that come after you in some levels.
Spear attacks can be quick to initiate but last a tad longer than other weapon attacks, which potentially exposes you to terrible enemy counter attacks.
*General rule of thumb is to avoid multiple enemies unless you have an overwhelming morale advantage

If you have been lucky and got dual sabers (that scale with earth) drop early, use those instead. Dual wield weapons attack faster, have shorter recovery animation, and also have good deflection efficiency** compared to single weapon.

What you lose out with dual wield is damage per hit - but it should be acceptable because doing just enough parries opens up enemies to "Fatal Strikes" - overcoming the per-hit damage disadvantage easily.

**Deflection efficiency, the higher the better - reduces spirit used when the parry/dodge button is clicked/inputted

Armors
Find and equip the highest Physical Resistance equipment you can. Keep an eye on the gear weight and keep it in green if possible. When it is yellow or red, your spirit regeneration becomes a huge problem (and you cannot parry while in red weight). Early on, the preorder bonus equipment will have the better stats, but by part 3/4, you will have better drops.

It should be obvious, but upgrade armor and weapons whenever you can.

DO NOT RELY ON SPELLS FOR DAMAGE
This is based purely on my current experience and It might be addressed in future updates or gears, but at the moment spells are pathetic in damage output.

Spells
Those spells are mandatory to improve your survival.

Earth - Enhanced Defense - Reduces damage taken, not be staggered by normal mob attacks.
Earth - Lion’s Roar (mastery required, unlocked by early-mid game side mission, be aware it also taunts enemies to attack you.)
Metal - Calamity Bolts - Reduces enemy attack, meaning you take less damage when hit by said enemy.
Wood - Absorb Vitality - Gain HP on attack, based on damage dealt <-- always use before backstabbing an enemy for max returns.

Nice to Have
Wood - Unstoppable Force - Increases passive spirit regen and high spirit duration.

The general tactics is to ALWAYS buff before a fight you know you will engage in, no matter how big or small. There is only a cool down period (due to spirit usage) for spells in Wo Long.

Having Enhanced Defense should allow you to take about 3 hits before dying; if the enemy has Calamity Bolts applied, as much as 5-6 hits (this all depends on the morale difference of course).

ALWAYS MAX YOUR MORALE
When possible always max your morale at 25 by exploring the map and capturing ALL flags (Battle and Marker) so that you start at 20 each time you die.

My estimate is each morale level difference is about 5% damage taken and dealt. That is a huge difference between dying in 1 hit and 2-3 hits while swinging once rather than 3 times to kill an enemy.

Skip cut-scenes if you buff yourself pre-fight; as spells seems to continue running while cut-scenes are playing.

Use Items wisely; they can be bought as supplies.
Bear's Gall - Increases spirit gain, stacks up to 5 uses.
Five Minerals Powder - Prevents morale loss on death; only 1 use per mission from what I can tell...

Learn your 5 Elements

Wood > Earth > Water > Fire > Metal > Wood

If you have earth-based buffs, those buffs will be removed when you take a hit from a wood element attack (Yeah, I learned it the hard way fighting Dong Zhuo).

That being said, the same rules also applies to your enemies - so learning and casting elemental attacks your enemies are weak against is also a bonus.

It sucks to die, but each time you die, you need to learn why and figure out how to prevent it from repeating (hence the rote memory requirement).