Leaving aside that most of the aid is in military equipment and only some of it is financial support, after the war Ukraine will be able to support themselves just like they did before the war, particularly if the west does the right thing and gives them some of that Russian oligarch money they seized in order to rebuild.

Ukraine's economy didn't depend on their oil reserves before the war since Russia made sure they couldn't be tapped with the seizure of Crimea and creation of LNR/DNR, but as long as Ukraine gets their cut they'll still benefit as well if gas companies come and start pumping crude as long as oil continues to hold value.