I've read many times what Nazi Germany's greater plan was, but I don't remember seeing anywhere what they wanted to achieve with WWI, especially given Germany is seen as one of the main instigators of the conflict. Also, as a side question: Did they count on Austria-Hungary being defeated?
The german war goals were set in the "Septemberprogramm" by german chancellor Bethmann-Hollweg in semptember of 1914. They included territorial expansion in europe (annexation of the french briey area for coal, annexation of luxemburg, annexation of parts of the baltic area), colonial expansion (forming a large, continuous colonial empire in central africa), and generally breaking germanys isolation by totally changing the political map of europe through more informal means (an european economic union dominated by germany, making puppets out of france and belgium, strengthening austria-hungary and so on). Generally, they wanted to reverse cauchemar des coalitions and assert european hegemony.
One thing to note though: These wargoals were divined when the war had already started and the western front was still moving and the germans were succesfull. In the first days of the war nobody had exact plans on expanding, the german government was sincerely thinking they were just acting to defend themselves. We shouldn't think that the germans started the war with the plan to expand and to break the french, unlike Hitler did 25 years later. Of course, the actual thought process of Bethmann-Hollweg and the emperor is a different topic, and i won't expand on this more than necessary.
Edit: grammar
These answers I've given in the past should be pertinent; the September Programme has already been mentioned, and while it was not necessarily set in stone, German war aims revolved around it for much of the war, and it's provisions for the East were fulfilled at Brest-Litovsk in March, 1918. As for Austria-Hungary, following the Sixtus Note of 1917, Emperor Karl was forced to militarily and economically subordinate the Empire to Germany; in the future, Austria-Hungary would have basically been a German vassal.