What to upgrade

Two year old self-built:

32GB RAM (Ordered 16GB, 32GB shipped!)
Gigabyte Z390 Mobo
Gigabyte 1060 6GB
Samsung M.2 SSD 500GB
750W PSU
Corsair 280X Case

MSFS generally runs in the mid-20s with moderate-high video settings. Corsair case is a small form factor, so not sure if a full length, 3 fan card will fit.

Upgrade most bang for the buck??