Hypotheticals are fun, but unfortunately historians cannot guess on questions like these, we have to use the stuff that happened in the past. So let's use William the Conqueror, he became king of England in 1066. The first thing he did was try and secure the kingdom using military force. This took a few years. Next, he tried to institute a system of political order by putting people loyal to him in positions of power, both lay and ecclesiastic. Many locales did not appreciate this new regime and resisted, so William had to go back to securing the kingdom through military means again.

Once things settled down a little bit, William appointed new sheriffs (mostly new) to help him collect taxes, which went both to his supporters he put into local power and to the king to help finance his household and military operations. Along with this he had to implement a new system of coinage to help reinforce his position of power and to help track his wealth (England's coinage was known to be a little purer than Norman coinage). Now that the money is flowing, William wanted to make sure he was getting all he owed, so he surveyed his new kingdom. This was the famous Domesday project completed in 1086 that listed all the property holdings worth mentioning in England.

Unlike previous English kings, William also personally controlled a large portion of English lands. This allowed him to directly collect taxes rather than having it go through his subordinated first, and provided him with a physical place to consolidate his power, usually with castles and other defensive structures. In the middle ages, taxes were not only hard currency like silver and gold, it also included goods like grain, fish, or salt as well as military service in the forms of men, arms, or horses. With both currency and goods coming in, William grew rich in lands, property, and liquid wealth. He used this to fund his court and household, the center and lifeblood of the kingdom. Without a properly paid and fed retinue, William could not administer the kingdom efficiently, nor adequately protect the kingdom from invasion or rebellion. In times of famine, this surplus of money and goods could also be used to feed the people.

So, to say William understood the economic state of the realm as a modern head of state might is not accurate. For him, without physical security secured through military, diplomatic, and political might, nothing else mattered because he likely wouldn't be in power much longer anyways. For example, in the Angevin era Gascony was vital for the English economy because it gave them easier access to the Mediterranean trade routes. They could sail around Brittany and land on the coast and hop across to the Mediterranean Sea instead of having to go all the way around Spain, or hop across the channel and travel by land through Normandy and Aquitaine. King John lost almost all of the English continental holdings between 1202 and 1214, except for Gascony. England was able to hang on to it for another century or so, which greatly aided them in trade. So while John knew losing the continental holdings was disastrous, hanging onto Gascony helped to lessen the blow. But again, it came down to securing territory militarily and politically, then addressing any economic concerns; and since military conflict was fairly common, logistics like roads or urban infrastructure sometimes fell by the wayside. For example, the chronicle of Battle Abbey records that the funding of their buildings, financed by William I on the site of the Battle of Hastings, fell through after his death because his sons William Rufus and Robert Courthouse were too busy fighting each other over control of their father's lands.

This is obviously just the tip of the iceberg, and many of these points have been purposely generalized, but here are some sources that go into more detail:

1.Older but good. MM Postan. The medieval economy and society; an economic history of Britain, 1100-1500 (Univ. of CA, 1973)

2. Richard Marshall. The local merchants of Prato : small entrepreneurs in the late medieval economy (Johns Hopkins Univ., 1999)

3. Avner Greif. Institutions and the path to the modern economy : lessons from medieval trade (Cambridge, 2006)

4. J.L. Bolton. Money in the medieval English economy 973-1489 (Manchester Univ., 2012).

5. Gregory Milton. Market power : lordship, society, and economy in medieval Catalonia (1276-1313) (Palgrave, 2012).

Hope this helps a little. Happy Reading!