A truly effective Italian army would take a lot, as is the consensus here so far. An Italian army that performed somewhat better in World War II than it did historically? Considerably easier.
One possibility (to be followed by more tomorrow:
Mussolini had many failings as a war leader, but he, and Italy, would have done considerably better if he had understood one concept: Concentration of force. Italy had a limited amount of military power. It could conceivably do well if it concentrated that limited power on one objective in one portion of the war while its opponents were forced to divide their power. Italy never concentrated on one objective at any point in the war.
In the summer of 1940 they put far more logistical effort into preparing to invade Yugoslavia (a project Hitler vetoed) than they did into trying to take North Africa at a time when British weakness made that at least somewhat more possible. They were also looking at possibly trying to grab Corsica at that point, and sending some of their best aircraft to fight in the Battle of Britain--where they were laughably outclassed, rather than using them in an area that made sense for Italy, and where they would have made some difference because Britain couldn't spare their good stuff yet.
In the fall, they invaded Greece, which again diverted forces from North Africa. From then on they had to support forces bogged down in the Balkans. Add to that: They had troops fighting in the Soviet Union, a couple hundred thousand of them at the peak. Again, those guys had to be supplied from Italy's meager industry and meager raw materials.
Concentrate all of the Italian truck, aircraft and tank production on supplying North Africa and the Italians do better. That probably wouldn't change the shape of the war much though. They don't win, because logistically they can't. Winning means taking Egypt and that wasn't logistically possible for either the Italians or the German and Italians together. A more mobile Italian army would probably still get defeated by the first British offensive in North Africa, but it probably wouldn't get totally cut to pieces like it was historically. More of it would escape to fight again. They would probably still need German help, but with it they could probably do the desert see-saws that we saw historically, but with the Italians fighting somewhat more effectively. And when US Lend-Lease got massive in late 1942/early 1943 they would still be buried in an avalanche of metal.