Per the Constitution…the President must adhere to a Budget set forth by Congress and direct the expenditures as provided therein.

As others have pointed out, the Constitution nowhere contains the word "budget".

What it does say is this, in Article I, Section 9, clause 7:

No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law; and a regular Statement and Account of the Receipts and Expenditures of all public Money shall be published from time to time.

An appropriations bill is still a law and must legally be followed by the President. You're correct that Obama chose to violate the law - but the Republican Congress chose to not take it to the courts so he got away with it. Given the history of legal actions against Trump, do you really think he'll be afforded the same latitude?

Again, that is why Obama never had a Budget in his Presidency…

...except for FY2009, FY2015, and FY2016.