What's your plan for actually getting people into your gym? Different people respond to different things. If you say "anybody", the plan suggests you haven't really thought about this, and you're expecting people to just show up and stay engaged.
It would be helpful to do case studies. Pick a certain specific kind of person that you think you can market to, and come up with a plan to get them training with you. You can extrapolate a target demographic from such examples.