The new start level or level "0" is light level 750. I'd recommend making a new chracter, start off with The Red War campaign and do your weeklies. The sequential order of D2’s story is the following: The Red War > Curse of Osiris > Warmind > Forsaken > Shadowkeep.
90% of those campaign are solo or co-op if you have a friend. 10% has matchmaking included but you won’t always be matchmade.
You’ll earn gear from these missions as well as currencies and new questlines. These questlines end up introducing you to characters in the Tower. Think of questlines as an “individual challenge” to complete. Then you might notice that there are these bounties you can take from these characters. These two are basically the same, except questlines are usually longer and more difficult while bounties are easier. The completion of a bounty, tied specifically to that character, will give you tokens.
These vendor tokens can be given back to these characters in exchange for specific vendor gear. Zavala has strike-related gear, Shaxx has Crucible-related gear, Devrim Kay (Planetary Earth vendor) has Earth-related gear, etc.
The planets that you can visit hosts a few activities as well. All of them come with public events, lost sectors, and adventures. The completion of these activities will also reward you with gear and currencies. Public events are the more social, open world, natural co-op experience. Lost sectors are these tiny, mini-dungeons you can do which does not auto-matchmake you with. Adventures are more like side stories regarding the planet.
So everything nets you gear and you will most likely come to a point, “Oh my God, I have too much gear and what do all these numbers and variables even mean?” In this game, that 750 number you see, that’s your power level / light level (interchangeable, same meaning). That’s how strong you are and that dictates how much damage you can do and how much damage you can take. So, some activities will be more difficult, which recommends you to be a higher light level. You don’t have to be, but it’s recommended. The way you gain higher light is by doing these activities. You’ll get weapons and armor. The thing is, your entire loadout (weapons + armor) all have to increase in order to become higher light. Let’s say you have a primary, special, and power weapon at 760. Then all your armor is 760, except your helmet which is at 759. Your overall light level will be 759 because of that helmet. So if you’re thinking of dismantling that 765 helmet you get in your next activity because it looks horrific, just keep it for the sake of having higher light.
At some point, you will reach a light level where no activities are giving you higher light leveled gear. That’s because you’ve reached “the soft cap”. At this moment in the game, soft cap is at 900 LL. From there, you’ll need to choose activities that will give you “Powerful Gear”. You can see who/what can give you these by looking at your Destinations tab. As an example, you can obtain Powerful Gear in the Vanguard Strikes playlist. You do this by following and completing the challenge it states there. It will most likely be “Match the elemental burn and complete 3 strikes by doing so.”
What's the Elemental Burn? Well, the character you made, whether it’s a Titan, Hunter, or Warlock, all come with the same elemental subclass. This encompasses Solar, Void, and Arc. So when you select that Strike playlist, right before you hit “Join”, there will be these 3 circles that fade in on the left side. Each circle is a modifier that dictates how the gameplay will be like for that activity. The first circle is typically an elemental burn. So if it’s arc, choose an arc subclass and you’ll work towards obtaining that Powerful Gear. You’ll also do more damage. Read those modifiers as you can try to spec your loadout accordingly and complete this activity efficiently.
Now you might realize, if I’m doing strikes, and that bald headed blue vendor Vuzuvela guy gives bounties for doing these strikes, I can synergize my time efficiently to get more loot. Exactly. Do that. More loot and less time.
But there’s a wall for how much Powers Gear you can get, within a week. Take a look at what activities you can do, and when you complete them accordingly, and don’t see anymore activities that can get you Powerful Gear - congratulations, you’ll have to wait for the weekly reset.
Weekly reset is every Tuesday @ 10:00AM (PDT). New modifiers and new areas will get you Powerful Gear. The grind to max LL (950) is the objective. Once you’re there, you’re a powerful Guardian. Take a look at your Triumphs and Collections tab, you’ll see what you’ve earned and completed. You’ll see some Seals as well, which give you a labeled nameplate to show off your achievement in this game.
But the real kicker and endgame content is optimizing the loadout you want. You’ll see the following items in your armor: Resilience, Recovery, and Mobility. These are perks that dictate your survivability. More resilience is more health, more recovery is faster health regeneration, and mobility is not faster sprint speed. Mobility is actually how tight your turn speed is and how high your jump can go. Then you have these: Discipline, Intellect, and Strength. These are the perks that dictate your ability cooldowns. Higher discipline means your grenade will be available sooner, higher intellect means your super will regenerate faster, and higher strength means your melee will be available sooner. With armor 2.0 introduced, you can hunt for the gear you really want.
This covers all the gameplay need to knows.
In terms of what you can play with friends, it gets sort of weird. Planetary destinations? 3-man squad but you can have up to 9 players in an instance together. This can be really fun for public events such as Escalation Protocol on Mars. Strikes? 3-man squad. Raids? 6. Crucible? Max of 3-4-6, depending on which mode.