For many, the Christian doctrine of creation is one of those that is difficult to apply in daily life. It has a certain importance, to be sure, in providing a starting point for both the Bible and the universe, but is not as relevant as, say, prayer. However, there is a larger importance to this doctrine as well. The idea that God created the universe - leaving questions of method aside - is of fundamental importance when considering the basis for knowledge and even the possibility and value of human knowledge. Specifically, there are three consequences for epistemology stemming from this doctrine of creation: the universe is orderly; the universe has a purpose; knowledge is obtainable and valuable.
First, the universe is orderly. God made it to operate along certain rules - or at least we can formulate rules that describe its customary behavior, such as the laws of gravity and of motion. We can and do expect such behavior, based on our previous experience (both collective and personal). The rationalists of the Enlightenment posited that the entire universe was rather like an enormous clockwork; the God of such marvelous machinery could well have fashioned it and then left it to operate on its own. This is, perhaps, going rather too far; the psalmist says that God holds the world "in the palm of his hand", and Paul tells us that "in [Christ] all things are held together" (Col. 1:17). So then, God continually causes the universe to operate in predictable ways, although He may also "break" these "laws" in performing miracles.
Second, the universe has a purpose. If God made it, and continually holds it together, then He presumably had a reason. "The chief end of man is to glorify God and to serve Him forever"; by extension, that is arguably the purpose of the universe as a whole. "The creation is inseparable from the kingdom of Christ wherein lies its purpose" (A. Holmes in Contours of a World View). This purpose provides a direction to the course of the universe and to the decisions and deeds of man - either glorifying God or failing to do so; more generally, either in conformity to God's purpose or at cross purposes. Creation itself is good, as God proclaimed after each addition in Genesis 1.
This brings us to the last point: knowledge is obtainable and valuable. God surely has all knowledge of what He has made, including even such minutiae as the number of grains of sand on the beach. While it is not possible for man to acquire all knowledge - such as the number of sand grains - it is possible, because the universe is orderly, and because God made man in His own image as a knowing being - for man to acquire some knowledge. It is valuable and good for man to study creation; it is the handiwork of God, and reveals therefore certain aspects of its Maker's nature as well as its own. "The heavens declare the glory of God", and "His invisible nature, that is, His eternal power and divinity, have been made intelligible and clearly discernable in and through the things that have been made." There are, certainly, limits to the knowledge of God that can be derived directly from nature; it would be difficult, for instance, to find evidence for Christ's atoning work through a study of structural biology. However, it is possible to know, and to know about God; such knowledge is good indeed.
Belief in God as self-existent Creator and the universe as His handiwork provides, then, a basis for all knowledge and thought. As such, it is of immense philosophical value, and of great practical value as well - it assures that the universe does make sense, that there is a reason for it all, and that knowledge though at times difficult is always possible, and definitely of value.