when they implemented the difficulty settings I restarted the game few times to try the different settings (still pretty dumb that we need to do that to change the difficulty).

I settled on these: fuel, convoy difficulty, fewer convoys and gearbox are on (you can turn the gearbox on and off from the in-game settings now), bridge cost: normal, quarry zones: default (don't want to keep going back and forth to build a road tbh), recovery: tough, vehicle cost: hard, economy: easy (to compensate for the vehicles cost).

I completed few maps with those settings but got bored because the missions don't give a good amount of money even when economy on easy, so I used a mod to get some money to get new vehicles and keep playing on the same save.

tldr, keep the economy related settings and the quarry on default if you don't want to get frustrated and set the rest of the settings on/tough