Depends on how you define best. Ignoring culture shifting since forming Italy is by no means a hard enough thing to do to justify culture shifting which is pretty close to cheating imo.
Easiest would probably be Milan. Great ideas, High development, you start in the hre which means you dont have to wait for shadow kingdom, and your in a nice central position to take the required provinces.
Venice is always an interesting start you start as a merchant republic but the thing I like about them is despite being natural rivals of both Austria and the Ottomans you start in a prime position to neuter both of them early on leading to some interesting games. Genoa can theoretically do the same to the Ottomans albeit with a bit more difficulty considering its harder your a little smaller but you dont have to be arch enemies with Austria so its a bit of a trade off.
Savoy is the historical choice
Naples is in an interesting position but their ideas are meh from what I remember.
Florence is a like Milan but with less development.
Unfortunately you cant form Italy with popeman but if you just want to play in the region their always fun considering the shenanigans you can pull with the reformation and the easy alliances.
Any of the opms would be a challenge but if you really want a challenge go with Urbino their a vassal to the popeman so your going to have a hard time getting people to support your independence aside from what ever medium power they rival and to top it off your not in the Hre so you either have to put a hold on your northern expansion or take a risky move of not taking much land when you win independence and hope no one wars you before you can buddy up to the emperor enough to join the hre.
Easiest would probably be Milan. Great ideas, High development, you start in the hre which means you dont have to wait for shadow kingdom, and your in a nice central position to take the required provinces.
Venice is always an interesting start you start as a merchant republic but the thing I like about them is despite being natural rivals of both Austria and the Ottomans you start in a prime position to neuter both of them early on leading to some interesting games. Genoa can theoretically do the same to the Ottomans albeit with a bit more difficulty considering its harder your a little smaller but you dont have to be arch enemies with Austria so its a bit of a trade off.
Savoy is the historical choice
Naples is in an interesting position but their ideas are meh from what I remember.
Florence is a like Milan but with less development.
Unfortunately you cant form Italy with popeman but if you just want to play in the region their always fun considering the shenanigans you can pull with the reformation and the easy alliances.
Any of the opms would be a challenge but if you really want a challenge go with Urbino their a vassal to the popeman so your going to have a hard time getting people to support your independence aside from what ever medium power they rival and to top it off your not in the Hre so you either have to put a hold on your northern expansion or take a risky move of not taking much land when you win independence and hope no one wars you before you can buddy up to the emperor enough to join the hre.