That definitely depends upon what you consider "conservative" and what you consider "unnecessary".
I, for one, am an advocate of a Constitutionally conservative philosophy of government. Therefore, a government that seeks first and foremost to defend the Constitution that is the foundation of our country. So, considering the fact that our country was actually born in debt (to the French), I would say that "spending money it doesn't have" does not actually go against the Constitution. As long as this money is spent appropriately for the benefit of trade and defense.
Now, for "unnecessary military adventures", I would again have to look at the entire history of our nation, starting with the founding years. While we were still in debt to the French for their aid in the Revolutionary War, we went ahead and started the Indian Campaigns in 1790. We fought the Barbary Wars from 1801-1805 and again in 1815. Fought, be it limited, in the Stockton Expedition in Liberia in 1821. In 1835 and 1836, the US sent aid in support of the Texas Revolution. From 1837-1840, the US fought again with Canada. We sent another military expedition to Liberia in 1843, and sent Walker's Expedition to Nicaragua for five years from 1855-1860.
I could continue further, but I think you get the point. From the founding of our Nation, we were extremely militant and sent our boys all out in what people today would most likely deem "unnecessary military adventures". Thanks to those adventures, America thrived and boomed and became a true world superpower by 1915.