A rich running engine starts easy and idles smooth. That is all most folks want.
If you want good gas mileage, you must set the engine up (the entire engine, not just the fuel system) to run as close to ideal stoichiometric ratio as possible for as much of the operating range as possible.
When you stray from OEM equipment and settings, you become a field engineer, and need to do all your own research. Vehicle weight, rolling resistance of tires, normal engine speed at cruise, gear ratio, wind resistance, air filter size, crankcase pressure, manifold pressure, and a bunch of other parameters all have bearing on fuel burn, and none of these factors include carb or ignition design.
If you are just now starting out, you need to get the engine in top shape.
Do a compression check, correct as necessary
Eliminate excess slack in timing chain and gears
Do a complete tune up on wear parts (this includes overhauling the carb and setting all the internal adjustments to fact spec)
You need 20+ " of manifold vacuum at idle (correct for altitude above MSL) Correct an necessary to obtain.
Once you have baselined the engine, start tuning the distributor. There are excellent threads on distributor tuning in the CJ section (YJs are generally non tunable because most have FI, CJs all were available with carbs). Search distributor tuning in CJ section. You have to have some minimum tools if you are going to do this: A high quality timing light, a multi-meter, a vacuum gauge (also works as fuel pressure gauge), and a timing tape set. A
When you get the ignition working, then you address your carb. An exhaust gas analyzer is ideal, but with lots of work and trial and error, you can get it done by reading the plugs, and possibly by tapping into the O2 sensor with your multi-meter to read your mixture burn ratio.
Suspension lifts and oversize tires are gas burners, if you want them, you will burn more gas, but you should be able to significantly increase fuel efficiency over what you are getting. One thing, setting an engine to put out more power (without increasing compression ratio) ALWAYS burns more fuel.
All the things above are do-able, but will be a long term project. It took me over 4 months to totally go through my current Jeep and bring the eficiency back to where it was whan it left the factory, I was also getting 10 MPG when I bought my 4.2.
418 miles on 19 gallons of gas. Can't beat the BBD !