Second. Don't worry about a fuel system yet. Do the DIY intake, a free-er flowing exhaust, and some gauges. Coolant and trans filters won't hurt either. Like external ones.
For a fuel system: The air dog is just a better pump and better filtration. The restriction is in the fuel rails. From the filter it either gets returned to the tank if it's over the regulated pressure or goes into the fuel rails. But out of the filter bowl into the rails, that's it. So you can get air in there and not exactly keep high enough pressure in there when you start demanding more and more of your injectors.
DIY Fuel System
Sinister Diesel 7.3L "Bowl Delete" Regulated Return Kit
Home Brew Fuel System for my Early 99 Powerstroke Turbo Diesel
That's just kind of a brief look into it. I'm putting a bigger fuel pick up tube in the tank (5/8th", also from Sinister), that size line to the first filter, then out to two stock fuel pumps (or one big Fuel Lab pump or the like), then into the next filter, out to the fuel rails, THEN into the regulator. That's the big difference. Stock is regulator then rails. Upgraded is opposite. So your injectors always have your desired fuel PSI.