Algernon is definitely a character who values style over substance. As such, we could describe him as an aesthete or a dandy, as another reviewer mentioned.
First, it is clear that Algernon prioritizes pleasure and is very self-centered. He enjoys the finer things in life. Algy is also willing to put his own desires above those of anyone else. For example, he eats all of the cucumber sandwiches that were made expressly for his Aunt Augusta (Lady Bracknell) before she even arrives, but he won't let Jack have any. At the end of Act Two, once the men have been "found out," Algy eats muffins to quell his own unhappiness, but again, he doesn't want Jack to have any. In other parts of the play, we see Algernon commenting on fashion, appearances, and fine dining.
Algernon primarily channels his aesthetic energies into his creation of the Bunbury figure. Bunbury is "an invaluable permanent invalid" Algy has invented "in order that [he] may go down into the country whenever" he wants. Basically, he says Bunbury is ill to avoid social obligations and then goes to enjoy himself doing whatever he wants, namely getting into "scrapes." He puts one of his elaborate Bunbury performances into play when he goes to Jack's country home pretending to be Ernest in order to meet Cecily. Algy has a wardrobe particularly for the occasion, as he tells Lane to pack up "all the Bunbury suits" for his weekend adventure. After he has wreaked all sorts of havoc on Jack's life through this stunt, Algernon cares only for the pleasure and fun he has himself experienced. He tells Jack this has been "the most wonderful Bunbury I have ever had in my life."
It is clear that style and his own desires will come first for Algernon. His appreciation of fine food and drink and his interest in fashion put him in the category of an aesthete. Further, his performance as Ernest and his play with the idea of Bunbury contribute to this idea that his life is a work of art to be appreciated and looked at rather than lived at a substantial level.