I can understand your delight at purchasing a VSL package. And it would be tempting to use them all at once!
Martin has given you a great set of examples to help you on the way.
It's worth noting the following.
In general, western classical music is based on 4 part harmony, in relation to your enquiry about chords.
When you set out an exercise or piece, i suggest you use individual instruments first. (Single violin, Single viola etc.) This is for two reasons.
The first is hearing just how the strings fit together as a group. for example, if you write the cello with notes on or above middle C, you are using the upper strings of the instrument, and they sound different to the lower stirngs. (The upper strings of the cello are generally considered to be the 'melody' strings, although in reality the cello has a great collection of subtle tones across the entire instrument)
In general, particularly when you're starting out, it's good to set your harmony in the natural order of instruments. From the bottom up--Contrabass, Cello, Viola, Violin. For the purpose of an example, consider the contrabass as rested at the moment.
So the 'bass' is Cello. The tenor is viola, the alto is second violins, and the soporano is 1st violin.
It's not really a good idea at this stage to consider splitting the harmony further, for all the reasons that Martin so skillfully explained.
It may be a good idea to refer to Horse Opera's thread entitled 'Berlioz Strauss treatise', in there you'll find some great comments from experienced composers, Martin, Dave Connor, Paul Robbins, etc. I've also incuded a couple of exercises that may help give you an idea of harmonic structure, and where to place instruments.
Reason two.
It's a lot easier to hear what's going on with individual instruments with reference to harmony. When you set up a chord, you can hear quite clearly what works and doesn't. Martin's point about divisi holds very true in this instance. splitting chords in a section weakens the balance of a section compared to the others. There is a reason why there are a balance of numbers in sections according to the dynamic overall. It takes a bit of experience and a lot of experimenting to balance divisi chords.
So if you stick to one note per section for now, and set up your harmony with individual instruments first, when you have a good balance of pitch and harmony within your 'test quartet', substitute the individual instruments for sections, and you'll have a much better result to go on with. Harmony works best, in general, when it's 'clean', i.e. uncluttered with multiple additional notes. Too many notes in a harmonic block produces a grey sound, and cancels out the tone of the collection. (In general).
Two books that are packed with useful information are
Treatise on Instrumentation by Berlioz (and Strauss)
Principles of Orchestration by Nikolai Rimsky Korsakov. (I consider this one a must in the orchestration reference library)
Good luck, and i suggest you search this site thoroughly. There are many useful threads that will help and give you important clues in your quest for excellence.
Regards,
Alex.