Mussolini's Popolo d'Italia was somewhat of a "metropolitan" newspaper. Formed as an "interventionist" voice, it kept this fundamental imprint throughout the Great War and, at least, for a few months after. That said, Mussolini didn't wish for it to be a mere propaganda instrument, or one of the many short lived publications, little more than a leaflet, born in the aftermath of the declarations of war, but to make it into a proper, perhaps even a bit "posh", press outlet. Whether he achieved this goal eventually came to depend largely on the fluctuating availability of funds, but it certainly helped provide an impulse towards a wider, national and "international" tone, which was somewhat uncommon for the Italian press of the time (except for a few bigger newspapers). The war itself contributed to this process, increasing the public's demand for international news. But it's still significant that Mussolini bothered with real correspondents as much as possible (until the War of Libya in 1911-12, most Italian newspapers had relied on official press statements, such as those provided by the Italian Stefani, or by the Havas). The fact that it was based in Milan - even at the time, and despite the fact that it could not aspire to compete with the main voice of the Milanese press of the time, Albertini's Corriere della Sera - added a further layer to this "generalist" attitude.

As a consequence, while Mussolini's angle remained somewhat consistent (I am at least assuming that you mean to focus on the period when Mussolini was actually chief editor of the Popolo d'Italia - otherwise the newspaper ran from 1914 to 1943, and that's a very long period of time for consistency) the topics covered varied with time. From the events of the war, to internal and international politics, with a special focus on organized labors and the various misfortunes of the "official" socialists, from local news to advertisement.

The newspaper is actually available online (almost) in its entirety - albeit not translated. If you trust my (very poor) translation skills, I have posted various excerpts from it around here, even if I'd be wary of picking one specific excerpt as representative, given the vast range of topics covered. Also, it is to be noted that Mussolini, besided contributing a few commentaries and redaction notes, as well as frequent opinion pieces, was a rather "hands on" chief editor: except for the times when he was serving during WW1, you can assume that every word printed had been approved more or less directly by him.

A brief examination of one random issue may nonetheless give us some idea of its structure. Let's try the issue of February 18^th 1919, page 1 - page 2 - page 3 - page 4

The newspaper had, indeed, usually four pages (some times six). Which was fairly common at the time. It cost 10 cent per issue - 28 Lire per yearly subscription. 48 Francs abroad.

Commercial and private ads run from 2 to 5 Lire per line.

From the Summer of 1919, the Popolo d'Italia had its own monthly "sunday special", Ardita, an attempt at an elegant periodical, going for 1. Lire each.

Page 1, top left: Mussolini's leading peace "Against the returning beast" - that of "neutralism-defeatism", especially of socialist and Bolshevik imprint. A political opinion piece, framed in the contemporary polemics with the official socialists and the various forces accused of undermining the Italian victory.

Center-left, and partly censored (press censorship established during the war remained for the most part active until the early summer of 1919), a declaration from an association of "fathers of the fallen" against the proposals of an amnesty for deserters.

Middle top, news from Trieste, detailing the "fights and contrasts in the mosaic of peoples", especially the "issue of the borders of Yugoslavia", of special interest for the Italian "national" public.

Right: international news, with an examination of the "new arminsitce terms imposed to Germany".

Bottom right: a corsivo (a column) by Arros (Arturo Rossato), of unusually moderate tone, on the hypocrisy of the German speaking notables of Trent returning to their ordinary life in the now officially Italian city.

Page 2: local news from Milan. A socialist "parade". Debates over the eight hours workday. Various initiatives in favor of veterans. A fourteen years old went missing. Job listings. Shows. Markets. Bonds advertisement. Local ads in the right third.

Page 3, top left and middle: A long opinion piece on the need for a "new style in modern theatre".

Center and Middle-right: bits of international politics, from Weimar and a Vatican attempt to reconcile with France.

Bottom-right: a Milanese corsivo, on the contradictions of the socialist administration of the city.

Page 4, top left: "latest" from Rome, that is national political news. Also, "Trieste vs. Hamburg", likely discussing the economical adjustments of post war commercial fluxes from central Europe.

Center: international news, usually official correspondances, from London, Paris, Rome and Zurich.

Middle-bottom: bits of incoming news.

Right: advertisement and publishing information.

If you want to read through some translated portions, see for instance this post, as well as check the Sunday Showcase.