get all your cas and bombers into ethiopia, dont send the fighters it will only be a waste of fuel, when your bombers arrive, put them on cas and bombing missions, send all your troops to ethiopia, send the mountaneers north and the tanks south, the rest of the units doesnt matter, but send all of them, setup a frontline and a ofensive plan but dont attack yet, wait for the event that gives you the attack buff and build planning during that time, when the event appears, select the 15% attack against ethiopia and use the battleplan to advance while giving small corrections to the units, rush ethiopia as quickly as possible, you will be able to capitulate them before they select the country to go into exile and get a peace deal, annex all of ethiopia
while this is happening, rush to the extra research slot, after that go for the ministry of italian africa and the new emperor of ethiopia focus, then release italian east africa and disband the irregulars (dont call italian east africa into the war)
when you unlock the balance of power thingy, get the factory output and research speed buffs that you can give mussolini, its not much, but it helps
after that you can do whatever really, some things i like to do
use the 50% plane research with the designer and the industry liasons air spirit to rush fighter 2
the prospect for oil and libyan refineries focus are great to have your own oil source
go for the steel industry in terni and strengthen northen industry to upgrade your designers
if you go historical and ally to germany, you probably wont even need tanks, just make a holding division with 12w and an engineer to hold the ports (i like to have 72 of these and spread across the med as im conquering stuff), a 24w 9 inf 2 arty template to push (48 of these are more than enough, put 12 on the french border on europe, 12 on the french border in north africa, 12 on the british border in africa and the other 12 you can use to whatever really lol), and get 40w 14inf/4arty marines for the naval invasions in the med, the Forza Navale Speciale focus is great because it increases your special forces by 2% before the war, after the war starts, you can go for the bersaglieri, divisione alpine and fanti dell'Aria focuses for a total of +9% special forces capacity, givin you a total of around 21% special forces capacity if you researched the Expanded Special Forces Program
the only tank you need is a medium flame tank support company for the attack bonus they give you, if you want to build them dont forget to rush engineers 2 and get the 38 medium tanks
build civs until around november 37, then go for mils while building some refineries for the rubber for the planes
i dont know how much you know about navy, but make some Light Cruisers with only medium batteries for the main fleet and make some anti subarine destroyers to convoy escort, you can make some subs to convoy raid aswell
some things that are good to build before the war, radar across the med for the extra detection, air fields in tripoli and derna, one naval base in north africa on each border, right on the border, and then make a lvl2 railway across north africa
if you go historical, enter the war as soon as possible and rush into french algiers and french morocco, dont use flame tanks on these troops as you will have supply issues in north africa specially around tunisia, you need to get the port and airbase in algiers, it makes naval invading gibraltar way easier later on
when invading egypt, if you get bogged down around el alamein because of supply, build another naval base in marsa matruh and a lvl 2 rainway connecting it from lybia
edit: this is not the perfect italian ultra min max guide, but this is what i like to do and it always works