Great advice above, so I'll just offer some guidance on terminology:
1-"VST" is a plugin format(like AAX or AU)
2-the plugins described above are "VI" plugins(Virtual Instrument)
3-Pro Tools cannot use VST plugins directly(but can use many with a "wrapper" or "host" plugin, such as Blue Cat's Patchwork(handy for when a plugin is not available in AAX format).
4-look for videos on all those plugins(maker's websites or youtube) to see how to get the most out of them(as said, how you "play" them will make a big difference).
5-Toontrack's EZBass is pretty killer if you need bass on your stuff(wonder if they have an EZGuitar plugin in the works
)