upstart: a person who has suddenly risen to a higher economic status but has not gained social acceptance of others in that class；
野心家,新贵,暴发户/不择手段向上爬的,投机专营的

An "arriviste" is someone who is just beginning to "arrive," in the sense of achieving success or making a name for oneself. Often the word can have slightly negative connotations, indicating a person who is highly aggressive or perhaps unscrupulous in his or her climb to the top. Like its synonym "parvenu," "arriviste" can also indicate a lack of certainty or confidence in one's newfound position. "Arriviste" is something of a new arrival itself, relatively speaking. English speakers borrowed the term from French in the early 20th century.

Examples:
The present consumption behaviour of female in China is of the following characteristics: arriviste consumption after inhibition, conflicting and symbolizing consumption.
She had more respect for Michaelis, on whose name they all poured such withering contempt, as a little mongrel arriviste, and uneducated Bounder of the worst sort.