Now that the system software allows you to, you should get a external USB3 HD for your PS4, at least 4TB, as after formatting that's reduced to around 3.65 TB.....I bought a 8TB HD at Xmas and have already filled 1TB of it just purely with games in 4 months.
I'd had to delete 18 games off my 1TB PS4 prior to getting the 8TB HD, and once a HD is around 15% from capacity it tends to slow down considerably anyway, so it's also wise to have space on your main drive, just from a performance point of view.

As Cipher mentions above about why downloads are so big now days, GT Sports has had several updates and one of the last cause loss of game save data, so they produced a new one with a fix that and bundled all the previous updates into one massive 32GB update, that replaced all the old ones.....a bit of a shock when I saw it auto downloading.