John Egbert acquires and alchemizes a variety of outfits throughout the course of Homestuck.
Green Slime Ghost Shirt
John's original outfit, although technically not his oldest one. The white shirt, which John found at an Asian store, features the Green Slime Ghost, a creature that is some kind of spin-off of Slimer from Ghostbusters. He found a similar shirt with a blue ghost which he sends to Jade Harley as a birthday gift. John wears the shirt with a black belt, white shorts, and white shoes. It should be noted that this shirt is long-sleeved, as shown in a number of pages in the comic.
Spade Shirt
John wears this outfit prior to acquiring the Green Slime Ghost shirt. The medium-gray shirt features a darker gray spade in the middle. The rest of the outfit is the same as that worn with the Green Slime Ghost shirt. The spade is likely associated with John's interest in playing cards, even at a young age. Karkat Vantas sees this shirt when he first starts trolling John and takes it as a sign that John is his kismesis, although he later drops this sentiment and becomes friends with John.
Suit
A suit that John finds in a package in his Dad's room, clearly intended as a birthday present to him. It is a very simple two-button suit, white in color, with a notched lapel, accompanied by a white shirt, black tie, and shiny black shoes. Though John wears this suit for a while, eventually he experiments with alchemization and creates an array of new and more stylish outfits.
Green Slime Ghost Suit
John creates the Green Slime Ghost Suit by combining his Suit with his Green Slime Ghost Shirt in an && operation, costing him 3 Build Grist and 1 Shale. The suit very closely resembles the standard suit, except that the black tie is replaced with one in slime green and a Green Slime Ghost appears on the side in place of a pocket. He only wears it for a single page, though - it's pretty swanky, but he isn't completely satisfied with the wardrobe update yet.
Wise Guy Slime Suit
Now we're talking. John makes the Wise Guy Slime Suit by combining the Green Slime Ghost Suit with his Harry Anderson "Wise Guy" book in another && operation, this time costing 1 Build Grist, 5 Shale, and 10 Tar. This time the suit bears the teal color of the "Wise Guy" book, the shirt is black, and the buttons, formerly in black, are now rendered in a nice contrasting white. It is also filled with Wise Guy tricks such as cards in the sleeves. John has never demonstrated even the slightest control over these tricks.
Junior Ectobiologist's Lab Suit
John discovers the Junior Ectobiologist's Lab Suit in the Ectobiology Lab in the Veil. It consists of a slime-green Howie-style lab coat, a dark green shirt underneath and similar dark green pants, some snazzy yellow shoes, and a black belt with a Green Slime Ghost buckle. Surprisingly, it is tailor-made to John's proportions, even though he never visits the lab before finding it. It's possible that one of the Guardians made it for him, or that it was provided by Sburb automatically, though an explanation has never been given. The suit is similar to the lab coat that Mom wears, suggesting that it could be a result of alchemization with Mom's coat and another of John's outfits. Since Mom visits the same lab previously, this is not entirely improbable. The suit is also similar to the one that Grandpa is currently wearing. Karkat and Vriska Serket find the outfit exceptionally distasteful and are sure to let John know it.
Vriska's Outfit
An outfit John alchemizes with help from Vriska after she criticizes his Junior Ectobiologist's Lab Suit. It resembles her normal outfit, with a green jacket and a Green Slime Ghost on the t-shirt where she has her Scorpio symbol. He has a pair of Rocket Boots, or at least shoes that resemble them as he still uses his Rocket Pack after putting on this outfit. The Green Slime Ghost is darker on this outfit than any other.
Heir of Breath Outfit
John receives this "godhood" after being resurrected as his dream self when he is killed while napping on his Quest Bed, and he still has it when trolled by Karkat before the scratch. The outfit is almost all blue: a blue shirt with a breath logo in place of the Green Slime Ghost, slightly darker blue pants, a blue hood with a long point, and yellow-and-blue shoes. It symbolizes his role as the Heir of Breath. This was the fifth outfit John receives that was not alchemized in some way.