"Because we can and it's free"

That's it... just kill, loot, sell and buy (mostly on Basil).

That's essentially it. A lot of people don't pick up monster drops but the money all adds up over time. Basil is also a good way to not buy a shop and get a better price out of your stuff. But it is a bit tedious and not always successful. Eventually you will accumulate enough to get some decent gear. But with all the maple point events buying a 1.5k store isn't that hard.