But then what about extensions? It's hard to find a good sound with FL Studio's default stuff.
(It's very clear that something like Nexus is out of my reach).
3xosc alone can make some huge sounds, however it really depends what you want to make. Each vst has it's advantages or disadvantages. Harmor, Massive, and Sytrus I heard are really good for making bass patches while Sylenth1 and Albino 3 I suppose are good for super saw or pluck sounds. Nexus has good sounds but my only problem with it is the lack of the ability to change the sound up, I typically use it for lower pad layers or it's choirs. You're also not going to go in sounding good instantly, it's going to be hard no matter what. I would suggest trying multiple amount of DAW/Plugin Demos and see what fits you the most. I personally like FL the best because it suites my workflow. There are a lot of free vsts that are good also like
T-Force Alpha Plus or
TAL NoiseMaker. Oh lord we haven't even hit the discussion of sample packs yet.