I'm primarily interested in why these smaller countries chose to join the war and what did they stand to gain from winning. I'm also interested in the lesser known theater of wars (Eastern front, African front, Asian front). THank you in advance!
For the Ottoman Empire, I would recommend taking a look at Mustafa Aksakal's The Ottoman Road to War in 1914. It is an in-depth account of how and why the Empire joined the War and joined it on the side of Central Powers. For more brief information, any introduction to modern Turkish / late Ottoman history by Feroz Ahmad or Erik-Jan Zürcher would do. Edward J. Erickson has some excellent in-depth work on the Ottoman Army, especially on the WW1. He has specific books devoted to Ottoman battles and fronts such as Gallipoli and Palestine.
For Italy, I suppose John Gooch's The Italian Army and the First World War might be what you are looking for. General histories like Martin Clark's Modern Italy: 1871 to Present will also be good for having a general idea. If you read Italian, the first volume of Renzo De Felice's biography of Benito Mussolini, Mussolini: il rivoluzionario, is excellent to show internal political and intellectual developments in Italy around the WW1, especially following the defeat of Caporetto. I can check my notes and refer you to specific parts of this 800-something-pages-long masterpiece if you read Italian!