Based on a lazy google search it seems he's never commented on the issue. But, come on, first ever AnCap president, there's no way he doesn't at least try and do something.
Also learned from google, apparently he's somewhat pro-gay right, but in the typical libertarian "mind your own business" way, which I guess is better than blatant bigotry 
Milei is the head of a party with virtually no representation in either legislative branch. But I have no idea how much power the President has relative to the Legislature, particularly in a country as fraught with fuckery as Argentina. I can't imagine there's a large coalition of deputies eager to ratify his zanier ideas. So it could be that Argentinans have simply elected themselves a period of prolonged legislative gridlock.
More likely Milei does a heel turn in office and aligns himself explicitly with a coalition of the bigger parties. And then he just does more bog-standard pro-business conservative fuckery, while the right-wing media sucks him off.
I'm sure he's going to come in and start firing all the last guy's ministers and then stacking the bureaucracy with as many dipshit Chicago School assholes as he can manage. If nothing else, this is going to be great for Libertarian sinecures. But as to how productive he's going to be as a policy maker? Idk. Its probably going to just boil down to breaking as much shit at the federal level as he can, in order to clear space for private businesses to claim another big chunk of the national economy and sink the national ledger into deeper receivership to its foreign creditors.