learn to use basic units like spears and archers well.

with Hungarians, you have jobbagies and szeks so you are better off than the rest.

all coastal provinces tech straight for ships (fort, port, keep, shipwright).

crank ships from at least 6 provinces and make a connected loop from baltic to the black sea.

upgrade trade like crazy.

right click on farming upgrades before trade gets online and see what income it will generate. if that is roughly 10 times the percentage of upgrade, then build, otherwise no.

don't build military units unless you have too.

have only 1 slav warrior as garrison in internal provinces.

use happiness buildings to provide rest of loyalty neessary to hike taxes.

check out MTW economics 101 thread in guides forum and the Hungarian guide there too. check out my Hungarian strat section to grab Venice early and how to secure a Huni empire in general.