Can you expand on the basic setup post & suggest some VSTs/soundfonts/etc? Thanks!
This could go on a while, I think others have done much better collections than I've done, but let's see...
These're everywhere, with various different states of price, quality, licensing etc. There's a tonne of free ones about. Good ones to start with are general GM collections. Here's a nice starter list (collected by 'darkesword') which has a few I've used before.
Other ones I like using are numerous retro game packs dotted about the place, Papelmedia, SGM, etc.
Good synths can be quite handy but also pretty expensive. Synth-1's been well recommended to me and a full filler for various kind of sounds from decent pads, acid bass & wubby dubstep noises. Dig around the web for preset packs to build up a good collection.
Other fun choices are emulators for various chips for the more authentic chiptune quality. i.e. '38911 Bytes' is a fun little C64 emulator. Just punch in the chip the console used for music synth followed by' VST' and you can usually find a few like this one for Sega Genesis/Mega Drive
Big fancy collections wot I use
For the more orchestral sounding things I'll often use the EWQL Play VST with various sound libraries I've bought from them. Recently I've also picked up Kontakt 5, which aside from coming with a decent collection of orchestral, synth, percussive & general misc voices, I also use Spitfire Audio's Albion (very 'cinematic' collection of orchestral voices) & Shreddage 2 for my obviously non-live guitarwork.
If you're into that sort've thing :p
Always handy to just build up big piles of samples. These're mostly useful for effects, percussions, loops etc.
Stuff FL Studio just comes with
Using the stuff that's shipped with your DAW of choice is a bit like using the Photoshop Lens Flare filter. It's fairly limiting, and anyone familiar with the program will know exactly what you're doing and call it unoriginal, but they can be a decent collection of stuff when getting started and I still occasionally drop an ol' FL Drumloop to enhance the drums a bit. Also has a few generators (though many are demo versions requiring many $$$s to get full versions of) that're pretty good.
Should be enough to get started? Generally you collect stuff and hear about stuff in an eternal unending pursuit of collecting until one day you find yourself buying a collection of Gregorian Chanting and wonder if you've gone too far...