You describe someone as a social climber when they try to get accepted into a higher social class by becoming friendly with people who belong to that class. 攀附上流社会的人
noun [专属名词]社交攀登者:试图在社交界获得更高社会地位或在时尚社会中获得认可的人。
That Rob was a snob and a social climber could not be denied. 那个罗布是个势利小人,喜欢攀龙附凤——无可否定。