Dallas Guy,

I think the main issue is not of money but of priorities, not of communication but of each other's language.

She wants to buy a house. A nice home and a good family is of utmost importance to most women. House is her priority.

You want to be a part of health club.  You want to stay fit and manage your weight problem.
You want to buy a guitar.  You love music and want to be a part of it. Health and music are your priorities.

Can you speak in her language and explain her that you value health and music exactly the way she values owning a house?

In case of arguments, don't try to be a 'fixer' (men tend to do so) but just listen.  There might be more reasons to why she doesn't want you to join a health club or buy a guitar.