In more modern Italian it would be "Non si preoccupò molto di accumulare ricchezze, ma lasciò una buona immagine di sé per la sua bontà", which could be translated as "He didn't pay much attention to accumulating wealth, but instead he left a good image of himself due to his goodness". It's quite archaic Italian, the verb "tesaurizzare" is similar to the noun "tesoro", the word for treasure, thus the verb means "to accumulate wealth". "De'" is an archaic version for the preposition "dei". "Premura" means attention, care, worry. Hope it helps!