IMHO, a team expects a top 11 pick to be good. Not necessarily hall of fame good or even all star good, but at least capable of being a 1-7 guy in the NBA.
So I think "gem" is misplaced. I like to use the word gem for the surprises, the late first round and the second round picks, or even undrafted players, who become solid NBA players or even stars. The 90s Blazers had loads: Terry Porter, Jerome Kersey, Kevin Duckworth, Clifford Robinson come to mind. Currently Tony Parker, Manu Ginobili, Monta Ellis. There are others but I haven't had my caffeine yet.