https://www.fullbucket.de/music/vst.html makes some awesome free synth emulaions, https://www.patreon.com/analogobsession makes hardware mixing emulations. You don't have to be a patreon to get his plugins either, he offers them free to everyone.
If you're still looking for VST's here are a few resources that are geared towards chip tunes, since that seems to be what you're interested in making. If you're looking for a one stop shop solution not just for chip music Native Instruments Komplete Start (which is free) should cover most of your needs .
Chip Music (Free) - https://woolyss.com/chipmusic-plugins.php
Chip Music (Paid) - https://www.plogue.com/index.html
Production Suite (Free) - https://www.native-instruments.com/en/products/komplete/bundles/komplete-start/
It depends on how far your are into your music-production journey, but for a few power tools:
Hi! As Slimepunk said it depends of how far you are willing to go.
For free there's a piano from soundpaint and a couple of free instruments too...
You have to install the sampler first and then the download manager.
https://soundpaint.com/collections/free-instruments
Spitfire Audio has LABS also have a great sounding collection of free instruments.
https://labs.spitfireaudio.com/?sortBy=prod_products_labs_popular
It'll be awesome if you tell what kind of music are you producing because libraries and VST's are not the same if you make survival horror music, orchestral or chiptune.
Cheers!
I also loved spitfire. For me it sounds great.
In case of chiptune there are free options if you make music on windows.
https://hiphopmakers.com/best-free-chiptune-vst-plugins
Some kontakt libraries also for chiptune:
https://impactsoundworks.com/product/insidious/
https://impactsoundworks.com/product/super-audio-boy/
https://impactsoundworks.com/product/super-audio-cart/
And also plogue has really great VST's (paid)
An alternative with plogue VST sforzando (free) is download soundfonts for using it into the soundfont sampler. But take care of some copyright issues.
https://musical-artifacts.com/artifacts?formats=sf2&tags=chiptune
