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!