Merriam-Webster's Eleventh Collegiate Dictionary (2003) offers this note distinguishing among various similar adjectives that might be applicable:
GAUDY, TAWDRY, GARISH, FLASHY, MERETRICIOUS mean vulgarly or cheaply showy. GAUDY implies a tasteless use of overly bright, often clashing colors or excessive ornamentation {circus performers in gaudy costumes}. TAWDRY applies to what is at once gaudy and cheap and sleazy {tawdry saloons}. GARISH describes what is distressingly or offensively bright {garish neon signs}. FLASHY implies an effect of brilliance quickly and easily seen to be shallow or vulgar {a flashy nightclub act}. MERETRICIOUS stresses falsity and may describe a tawdry show that beckons with a false allure or promise {a meretricious wasteland of casinos and bars}.
S.I. Hayakawa, Choose the Right Word (1968) offers this discussion of the same five-word family:
These words refer to tasteless displays of overdone finery or decoration, or to brazen, flaunting behavior. Of these words, gaudy is the least negative in tone, but still points to excessive use of decoration or to any sort of vividness that approaches vulgarity: ... Flashy is an informal substitute for gaudy, referring to anything deliberately chosen out of exuberantly vulgar ostentation: ...
With garish, the emphasis is wholly on extremely distasteful ostentation and more especially of phony or trashy gimmicks: ...
Meretricious and tawdry both emphasize decoration that is made of cheap or worthless materials.. With meretricious, the stress is on overuse, especially of phony or trashy gimmicks: ... Tawdry may, more simply, suggest cheapness combined with showiness in taste: ...
Of these options, gaudy and flashy seem the most applicable to the particular situation you describe.
One (gender-neutral) noun form that might fit the situation is vulgarian. MW's Eleventh Collegiate Dictionary offers this definition:
vulgarian a vulgar person
where vulgar may be understood to mean "lacking in cultivation, perception, or taste: COARSE" or "ostentatious or excessive in expenditure or display: PRETENTIOUS."