Most Helpful Girl
Most Helpful Guy
Normally, I advise guys to ask girls out immediately, but the gym is one of the few places that such a strategy can backfire on you. What I would do is walk up to her (when she's not in the middle of a workout of course), introduce yourself, then ask her something like whether she has been going to that gym for a long time. Then tell her it was a pleasure meeting her and leave her alone. If she's interested, she'll approach you when she's ready.