Start a monthly transfer of some money that goes directly into a savings account. Eventually that money will add up to something meaningful and you can then throw that money on your Z.
Realize that above all else, a project car is going to take two things: time and money.
Knowledge is also going to be needed, but that comes with time, so don't fret if you're not sure what to do now.
The best thing you can do is limit the scope of your project as much as you possibly can. If you're looking for a fun, weekend car, then just clean up any rust holes you can spot, replace the sound deadening with some dynamat like material or lizard skin, and figure out what you're going to replace your gas tank with, and put it back together.
Realize you don't NEED 300hp, you don't NEED coilovers, you don't NEED 17" wheels, you don't NEED massive brakes, and you don't NEED to have a world class paint job to really enjoy the car. Those are wants. If you can afford those wants (in both time and/or money) then do whatever you want to do.
Start by creating a spreadsheet of how much certain things are going to cost, and realize that things start to add up quickly, and try and be as through as you can. Fittings and other small things may not seem like much until you have to order a ton of them. Then make a no bullshit assessment on what you're comfortable with spending on something that you'll probably never see a return on investment.