Since he runs his operations privately, it is difficult to know everything he is invested in but it appears that everything he is promoting that is visible (along with his demands for government action) is usually tied up with massive personal investments made by him.
One sector where he has vast investments, that may be too difficult to hide since he has brought on too many billionaire buddies as partners, is the energy sector. With so many partners, something might leak so he is being a bit transparent about these investments.
He even mentions offhandedly his energy enterprise, Breakthrough Energy, in his new book and reports how he roped in his billionaire pals to join him, curiously, just before the Paris Agreement was signed: