While we can look of the Treaty of Brest-Litowsk for the Eastern Front (spoiler: huge territorial gains in the East for Germany) Some argue that Germany wasn't that interested in oversea colonies, because it viewed the Baltic and Eastern Europe as colonies as shown in the "Lebensraum" ideology of the NSDAP under Hitler. But that is a different debate.

The West is more tricky to answer. This was a decade long debate in post WW1 Germany, luckily for us in the 50s historians discovered the so called "Septemberprogramm" (September program) in the German archives. Written by the German Chancellor Hollweg on the 9th of September 1914 it outlines some of the possible outcomes of a German victory.

Before I start giving some points of the program please keep in mind, that this program doesn't reflect an official stance of the German government and certain ideas changed during the course of the war. This program itself is based on the ideas of different parts of German society, industry, military and politics. Some selected points of the program:

France. The military to decide whether we should demand cession of Belfort and western slopes of the Vosges, razing of fortresses and cession of coastal strip from Dunkirk to Boulogne.

The ore-field of Briey, which is necessary for the supply of ore for our industry, to be ceded in any case. Further, a war indemnity, to be paid in instalments; it must be high enough to prevent France from spending any considerable sums on armaments in the next 15-20 years.

Furthermore: a commercial treaty which makes France economically dependent on Germany, secures the French market for our exports and makes it possible to exclude British commerce from France. This treaty must secure for us financial and industrial freedom of movement in France in such fashion that German enterprises can no longer receive different treatment from French.

Belgium. Liége and Verviers to be attached to Prussia, a frontier strip of the province of Luxemburg to Luxemburg.

Question whether Antwerp, with a corridor to Liége, should also be annexed remains open.

At any rate Belgium, even it allowed to continue to exist as a state, must be reduced to a vassal state, must allow us to occupy any militarily important ports, must place her coast at our disposal in military respects, must become economically a German province. Given such a solution, which offers the advantages of annexation without its inescapable domestic political disadvantages, French Flanders with Dunkirk, Calais and Boulogne, where most of the population is Flemish, can without danger be attached to this unaltered Belgium. The competent quarters will have to judge the military value of this position against England.

Luxemburg. Will become a German federal state and will receive a strip of the present Belgian province of Luxemburg and perhaps the corner of Longwy.

Holland. It will have to be considered by what means and methods Holland can be brought into closer relationship with the German Empire.

In view of the Dutch character, this closer relationship must leave them free of any feeling of compulsion, must alter nothing in the Dutch way of life, and must also subject them to no new military obligations. Holland, then, must be left independent in externals, but be made internally dependent on us. Possibly one might consider an offensive and defensive alliance, to cover the colonies; in any case a close customs association, perhaps the cession of Antwerp to Holland in return for the right to keep a German garrison in the fortress of Antwerp and at the mouth of the Scheldt.

The question of colonial acquisitions, where the first aim is the creation of a continuous Central African colonial empire, will be considered later, as will that of the aims to be realised vis-à-vis Russia.

You can access the whole document in English here: http://www.wwnorton.com/college/history/ralph/workbook/ralprs34.htm

I also recommend the book of Fritz Fischer, "Germany's Aims in the First World War" . This was the cause of the Fischer-debate in German historical science whether the offensive or defensive character of the First World War im Germany in the 1950s.

Edit: excuse the format of this post. I wrote it on my mobile.

Many thanks, stranger!