Okay listen to me on this one, if a guy wants you he will make his intentions clear. You however, need to throw some bait at him so he bites. Ask him what he does on the weekends or outside of the gym, then see if he is doing anything that day and if not give him your number and say "If you think of something to do hit me up, I would love to join." it sends the sign that you are interested in him, and he won't think you are being too pushy because you are letting him set up the plans. Just don't be all over him if he isn't interested after your first hint, let the guy go if he isn't into you.
You're in luck! It's the gym. There's no setting where it is more socially acceptable to be in short, skin-tight apparel. Plus weightlifting boosts a guys testosterone level, making them aggressive and horny.
Above all, give him a subtle smile when you see him, then:
*Stretch in front of him
*Do butt bends in front of him.
*Exercise where doggy-style position and lift/extend one leg back
*no matter how much he's bicep curling, act like you're impressed by how heavy the weight is. When he's resting, reach up and squeeze his bicep and tell him, "wow, it's so hard."
Unless he's homo, or you're fat, that should do it.
Give him your number, ask him to get coffee or something. There's nothing wrong with a girl asking a guy one a casual date like getting coffee. Think about this too, some guys, even the buff ones that work out all the time may be shy. Sometimes guys really appreciate it when a girl initiates things because it takes pressure off of him. My ex asked me out and we were very happy for the year and a half we were together. It was her depression that made things go south. Anyway, just be forward with him and if he still doesn't bite as in call you, then move on.