It really depends on what you enjoyed about Homestuck. My favorite fanventure is Kittyquest, and if you want to read Kittyquest I really highly recommend reading the sort of prequel fics by the author (purplebard), which consist of the series "Pilot Light, Pale Rapture" on ao3. I agree with other commenters that you should read Detective Pony, because it was clearly an inspiration for the epilogues and for post-canon work. I also suggest Theatre of Coolty, which is a relatively short fic. Another good 'meta fic' would be "Backstage" by quartile, and its short sequel, "Backstage II: Rose on the Run".

If you have any particular tastes for specific types of fic (for example, what relationships do you enjoy? What genre, what pairings, what concepts?), I probably have a rec for you.