It is very easy when starting out to spend lots of money, sometimes not wisely.
One advantage with VSL is the wide range of possible writing styles.
IMO, when starting out the SE libraries can make a great deal of sense. It is a very inexpensive way to get the basic sounds of a full orchestra. The drawback is, that over time, one generally wants to upgrade to the full libraries. What complicates things a bit is that for the full libraries, in the end, one needs both the standard and the extended portions of the library, as the extended portion of each library really does help when seeking to emulate real instruments.
As for key libraries, perhaps AP strings (since you are interested in a larger sound), Woodwinds I, Brass I, and basic percussion (perhaps not the extended here). Given your goals, starting with key full libraries, even the standard portion only, might be the better way to go, since that is a clear goal.
As for software, do consider VI Pro as well, although it is less daunting to start with the free VI (and anything done in the free VI will transfer to VI Pro). VI Pro adds a great deal of flexilibity, particularly in terms of humanization and the stretching feature (to name two). The stretching feature will allow you to create different articulations (shorter and longer detaches, for one example). Particulary if you decide to start out with the SE libraries, VI Pro can help you create articulations to fill in some of the gaps, though it is even more valuable with the full libraries.
One option would be to buy the very minimum number of VSL libraries you need to start out, and then continue to save money in order to take advantage of one of the VSL special offers - VSL generally has special sample purchasing offers about twice a year or so. If you are a student, generally - though not always - there has been a student special about once a year, at the end of summer/early fall.