I'm thinking I can sell it for a 7dii and use the rest to invest in a prime lens which I'm missing in my collection.
5diii to 7dii?
Just buy an affordable but good prime and be done with it. One of the new IS primes os maybe a Sigma 35 or 50 should do it. If you shoot general photography, it's a loss to sell a full frame camera over a crop no matter how good that crop camera is.