Depending on your software load, you can get by with a much smaller SSD.
I've got a 40GB SSD with 19GB used. Just keep all of your data, pics, vids, files and folders on the spinners.
No problem, works great.
I have been doing this, at least in a different partition, with my HDDs for about 15 years. Can't figure out why everybody doesn't do this, makes re-imaging or re-installing the OS very easy.
No need to buy a big SSD for data storage, not yet anyway. When the prices really drop, say 500GB for $100 then maybe.
You can get a very nice 40-50GB SSD for $100 or less.