Diesel engines need air flow, especially under load.
Start with a new air intake and 4 inch exhaust. The head pipe on the Fords is 3 inches but it is not round but flattened out. Big difference to make these mods.
Then a tuner but be careful when towing and use engine mods designed to pull. It is a great idea to monitor the exhaust temperature.
All of these changes can be easily made in your driveway for around $1000.
I have gotten a high of 23.8 mpg with a one ton auto trans 7.3 liter engine. I have recovered that $1,000 many times.