I've only just tried the RM after playing, on other accounts, most other nations. RM destroyers, in my opinion, do not compete with those of the other nations; firstly, lacking in gunnery - Leone, with level 15 gunners, is able to command only 4x3.9-inch guns whereas even torpedo-oriented Kagero, with same-level gunners, will overwhelm it with 6x5-inch guns (in the form of three double-gun turrets). What's more, already vastly out-gunned, the RM DD lacks in torpedoes - able to mount only the light-weight, 17.7-inch dual-launcher available from level 12. This limits, if not eliminates, its ability to conduct the sort of high-risk (but high-reward) tactics used by other destroyers to penetrate enemy DD/CL screens and sink, via torpedo, larger but more lucrative ships - CA, BB, CV.
To SDE's credit, this relative weakness of RM destroyers is consistent with factual history; prior to World War II, most destroyers in service with the Italian navy being severely compromised as compared to those of their soon-to-be enemies (England, France, etc.). Even so, a number of Italian destroyers fought brave if hopeless actions in the Mediterranean during the war; Luca Tarigo (a Navigatori class) being one of them. In the battle of Tarigo Convoy, Tarigo torpedoed and sank the HMS Mohawk, even as Tarigo herself sank.
From a purely gameplay-perspective, I'd recommend retaining neutral gunners and utilizing a neutral DD (armed the best available 1-credit/free ammunition guns until you can buy the 6-inch singles) up until at least the Oriani (an NDD wielding 6-inch guns is more than a match for most nations' early DD classes). Better yet, level two operators (via NDD) up to the RM ECL - considered quite good - available one level later. Levelling two operators will ensure you have the credits to both buy and outfit the ship, whereas on one you will 'barely' be able to afford the hull. Two operators will also have you better prepared for keeping your supports at-level as you progress further up the ship-trees (alternating operators usually required to do so, with the added benefit of levelling your gunners, and allowing you access to guns, well ahead the level of your ship).