Started this game on vh tonight and i would definitely consider myself a casual player. This is the peace deal i'm considering atm. Kind of a humblebrag i guess?
"Strategy" involved Ottos taking the 'Conquer the last crusader bastion' mission where they fought a funny war against The Knights where they didn't even set a foot on Rhodes and only white peaced them and cyprus after taking some land from Venice who had guaranteed The Knights. I tried to snipe a good island/strait block during this war but didn't see a good enough chance. At one point The Turks got into some weird loop where they kept splitting their troops in Sugla in order to (i guess) go to Rhodes using their transports that sat in the Aegean Sea but the troops never moved. Just kept splitting and merging until the white peace.
Anyhow a bit after or during (can't remember) that war i secured Hungary as an ally and declared a reconquest on Selanik which had a mothballed fort. Few months after i declared The Mamluks did as well and we've been pounding the Ottos ever since.
My other ally was Trebizond who distracted Ottos on their side a bit and Wallachia who joined once i got 10 favors on them. Didnt probably even need them at this point anymore, but felt bad and invited them in on the fun.
On vh they have quite the navy superiority in the beginning so i didnt see a chance for an earlier wardec, though it might be entirely possible to someone more experienced. When i declared (1454) they had already fought a few naval battles with Venice and my 2 queued heavies were almost ready so i felt confident enough at least navally.
Of course i'm not entirely out of the bag yet but i'm hoping i can secure some more/better allies during the long truce we are gonna have and i bet The Mamluks are gonna gimp the Turks some in their war too.
So to conclude: a bit of luck so the Ottos don't attack you first, 2 savescums (damn you Hungary ai) and a few careful (lucky?) battles got me thus far at least.