What XXSockXX said.
FL Studio nowadays sports a ton of features that makes it kind of top of the line, such as live performance for use with Novation Launchpads and its ilk, and as was stated, flexibility in terms of VSTs. Make no mistake that FL's default synthesizers are crap; a vast majority of the purchaseable ones such as Harmless and Harmor, a pair of additive synths, are capable of making things ranging from an E-piano to a Dubstep wub.
You'll have to go out of your way to find acoustic VSTs if that's your thing though.
Well, I'd like to try out all sorts of different styles, but mostly i plan on using Acid Trance and rock/soft-rock the most...if that helps round down recommendations, I apologize for not being specific,but like i said: Even i am unsure of what exactly I'm looking for past the ability to make those music styles.
You can do any music style with any DAW if you know what you're doing. FL Studio for example was initially designed with electronic music styles in mind, but you can find a ton of examples on youtube of people doing anything from orchestral music to extreme metal with it.
You basically just have to find VST plugins (synths and effects) and/or samples you like and then go from there. If you can play guitar, you can record yourself and use that, synthesized guitars are getting better, but the'yre not quite there yet IMHO, at least if you're looking for something easy to use and free.
To get started it's probably easiest to begin with the built-in plugins, make some beats, basslines and melodies to get a feel for how it works. Then you can search the net for VST synths or sample banks (WAV or Soundfonts or anything that is supported), there is more free stuff than you can ever use, for any kind of sound you want. Or record stuff yourself and use that, there is no limit really in what you can do.