What were the most significant aspects of Alexander’s legacy (in terms of kingship and military command) immediately after his death for the Macedonians? How did this change in the 50 or so years after his death?

First, before the rise of King Philip II of Macedon (380–336 BC), Macedonia was a fairly minor kingdom that was regarded as backward and insignificant by its neighbors. The rise of Philip and Alexander turned Macedonia into a well-known multinational empire through the conquest of the great realms of Egypt and Persia, the unification of Greece, and even the extension of power to India. This conquest brought great wealth and power to the Macedonians. It also gave rise to a cosmopolitan Hellenistic culture that was predominantly Greek but borrowed freely from Persian and Egyptian traditions.
Perhaps one of the most important effects on Macedonian soldiers was the institution known as cleruchy (based on an earlier form of Athenian colonialism), in which soldiers were offered plots of fertile farmland, especially in Egypt, in return for their service. This did two things: first, it gave soldiers an incentive to be loyal and stay in the army in order to become wealthy landowners on retirement. Second, it established a cosmopolitan Hellenized class of landowners throughout the areas Alexander conquered.
Alexander was an innovative commander who inspired loyalty not only in Macedonians, but also in recently conquered barbarians. They were able to enlist in his armies, something that became a tradition in his successor states. Next, his army had a far larger proportion of cavalry than previous Greek armies, something that again changed military strategy, as did his use of the Macedonian phalanx. He copied many of the administrative and logistical innovations of the Persians in running his empire.
After his death, there was no clear succession plan, and the territories he conquered were split into three empires, the Seleucid in the east, the Ptolemaic in Egypt, and the Antigonid in Greece. Although these states eventually collapsed, the cultures and administrative innovations of Alexander continued on. Perhaps the most important innovation for the average Macedonian was the Hellenization of their world and the sense of being part of a cosmopolitan Greek culture.