Any advice on finding hard working and dedicated staff?

I missed the part of the question that we are talking about personal trainers only, sorry.
Pay more than your competitors if they are going to be employees. Offer bonuses.
If they are going to be independent contractors, have a better split than industry average (which is 50/50). Offer bonuses or a fee split graduation system.
If it’s a rent/fee situation charge less than your competitors, until you get enough monthly trainers.
Make sure what you are providing is better (or cheaper by comparison) than others.
Make sure the facility is clean, orderly and everything is in working order.