Transitioning from Rent to Own

[Clifonef]

I am a newbie, but interested in doing some cold water diving.  I am relatively short, so off-the-rack wet suits are decidedly long. 

If I want to get to the point where I am not bound to go to a dive shop every time I dive, what would be the best progression of buying equipment?

Also, in terms of expense, which items is it most economical to own vs. economical to rent?

Thanks