Well you're going to have to read it anyways. I'm only giving you the basic plot outline to help you get along and understand the story to an extent.

So BASICALLY
Homestuck begins when John Egbert receives a beta copy of an upcoming game, called "Sburb," in the mail. Installing and running the game on his computer triggers a meteor attack on his real-life house, which survives only by being transported to another planet, thus immersing him completely within the world of Sburb. As John's friends Rose Lalonde, Dave Strider, and Jade Harley join the game with him, they learn that they have unwittingly triggered the end of the world, and that it is their duty to play the game and thereby see the story through to its completion. They have no choice but victory, for if they fail they will be trapped in the game forever.

As they begin to explore the world of Sburb, John and his friends are harassed by a group of twelve internet trolls who have played the game before. Further contact with the trolls reveals that they are not human at all, but an alien species actually called trolls. More is revealed about them and the world of SBURB until the first Intermisison of the story hits, known by most fans as THE Intermission for it was the first one it had the most impact.

The Intermission starts with Spades Slick (An alternate version of the arch-agent of Derse-Jack Noir who the kids had come in contact with before) in a green mansion. It is explained that he is here with the Midnight Crew (his own mafia made up of his friend Club Deuce, a demolitions expert, Diamonds Droog, a weapons expert and very handy with fashion. Always dressed to kill, and Hearts Boxcars, the muscle of the team.) They are here to kill all of a rival gang called The Felt (which are themed after pool, and are also lead by Lord English) for they have been trespassing on their city.

These rival gang members all have their own special powers, listed in order from member to member:
1-Itchy-Can slow down time around him
2-Doze-Can slow down time for himself
3-Trace-Can see people's past trails aka where people have been and what they have done
4-Clover-Is incredibly lucky, and apperntly he can fly but it is not proven in canon
5-Fin-Can see people's future trails aka see where people are going and what they will do. The exact opposite of Trace's power and vise versa.
6-Die-Uses a Voodoo doll to teleport to different timelines. Each of his pins represent a different person and if he sticks their pin in he goes into a timeline in which they are dead. He has pins for all The Felt and Midnight Crew.
7-Crowbar-His crowbar can break anything-even Juju's.
8-Sn0wman-Her life is tied to that of the universe. If she dies, the universe dies. And vise versa.
9-Sitch-Uses effeges to fix up the members of The Felt. If someone's article of clothing is on the effeege it becomes theirs.
10-Sawbuck-If he is hit or if someone hits him, both are transported to a random point in time. He is also very hard to kill.
11-Matchsticks-Can travel through time through fire.
12-Eggs-Uses an egg timer to pull of a clone of himself from one hour from the future.
13-Biscuits-Is Eggs' partner and almost absoloutly useless without him. He has an oven which he believes can be used for timetravel but in reality it appears to do nothing at all. Alone he is not a threat, but with Eggs they are an almost unstoppable force.
14-Quarters-Is part of the muscle of The Felt, Along with Cans. He has a set of Quarters and each side of the coins corrospond to a different member of The Felt. If you flip a Quarter and get a member of The Felt other than you, they appear right next to you no matter where thet came from, if you get your own number, you die.
15-Cans-An almost unstoppable killing machine. Built like a tank and as big as a wall. He can quite literally punch you into next week, and if he really wants to punch you oput of the entire calender year.

Now, as the trolls gradually become more important to the story, the narrative shifts to a side story exploring the nature of troll society and the specific sequence of events that led to these particular trolls entering the game themselves. The trolls' arc concludes with the revelation that winning the game causes the creation of a new universe, and that it was the trolls who originally created the humans' universe.

The story returns to focus on the humans. Increased contact between the humans and the trolls leads to an uneasy friendship between the two groups, as well as the discovery that they must cooperate to try to salvage the kids' doomed game session. They learn that the game has a mechanism for restarting, called a "scratch," and they begin working toward the ability to activate it. Fighting against them is a rogue non-player character within Sburb, called Jack Noir, who is nearly invincible (this will be explained how he became this way later), and unique to their session, as the trolls had formed an alliance with their own Jack Noir (Who then became Spades Slick). Despite this obstacle, the kids narrowly manage to trigger the scratch, which results in the destruction of the kids' universe - though the players themselves survive by traveling through pocket dimensions that will lead them to the new session.

The scratch causes the humans' universe to restart, with the condition that the kids' guardians are the ones to play through Sburb now, not the kids themselves. John's grandmother, Jane Crocker, who had died before the story began, is now a fifteen-year-old and the protagonist of this new arc, and leads her three friends, Roxy Lalonde, Dirk Strider and Jake English, through their own session. The trolls has a restar as well, and now their ancestors were the ones who also played. Though they all have died before anyone found out about them. Meanwhile, the original humans and surviving trolls must journey to the new universe over the course of three years, in order to aid the new session and bring it to completion. Threatening their plan is a villainous creature called Lord English, a purportedly invincible time-controlling demon, as well as the still-dangerous Jack Noir. The stakes are at their highest, with multiple groups of both humans and trolls forced into a race against time to discover a method of destroying Lord English before he potentially destroys all of existence.