For Gates, Expanders, Limiters and Compressors I use a wide variety of VSTs, including the actual FL Multiband (though usually only for simple or veen mastering compression). BlockFish, FloorFish, and SpitFish are a good set for ease of use and they produce some good toning and warmth. But I also interchange Endorphin and Dominion for various modelling tasks, as both have their place in the scheme of things too. And let's not ever forget UltraFunk FX whole set of VST FX, including it's compressor setup. Wow...without UltraFunk I'd be lost sometimes.
As for VSTi's from various artists, if you like someone's instruments, send them a PM asking what they used. Most of the Audio Portal musicians, I'm sure, wouldn't mind giving you a list of their VSTis, and if they're freeware or shareware VSTis, some might even shuttle one or two to you or at least point you to where they dl'ed them. As for samples, some people use sample packs, some use soundfonts, and some of us find great breakbeats or solos and chop them up into our own sample packs. So, it's a mixed bag as to how someone got their sound and I've known some people who guarded their sample secrets pretty closely.
Hope that helps with the compression and VST question.
Peace