It was Quins' third successive victory and director of rugby Richards said: "It gives an indication of how good the side could be. There's not many people under 25 in that side."
Harlequins have emerged from a dismal end to 2007 to mount a challenge for a Premiership play-off place.
Richards added: "It's a great result in terms of setting our stall out playing against the best in England.
"Gloucester play a great brand of rugby but we persevered right through to the end. It was a difficult time in November and December but we had a break and took a few things back to basics.
"I have a great team here - not only on the pitch but the support team as well and the coaches never lost their confidence in the players."
Richards also promoted the England claims of full-back Mike Brown, whose late first-half try kept Harlequins in contention when the game appeared to be slipping way from them.
"I thought Browny played very well. He should be pretty close to an England spot," he said.
Gloucester head coach Dean Ryan refused to blame his misfiring goal-kicker Willie Walker, who landed only two kicks from seven attempts.
"There were lots of opportunities were we should have won the game and we didn't. You can't blame the kicker," he said.
"Our game management wasn't really good enough and we got pulled into a fragmented game which we didn't want.
"As a group we should have done better. That was the disappointing element."
He added: "We had more control and more opportunities but we lost a little but of clarity about what it is we are trying to do."
A malfunctioning line-out added to Gloucester's problem and Ryan admitted: "We are not good enough in that area. It added to the fragmented nature of the game."