4. Custodian of holy cities (1493 - 1507)
Tunis is attacked for two reasons - first of all they're already at war, helping Morocco against Castile and Morocco won't honor the defensive call to arms and even more important reason is that our AE is non-existent with Berbers so they're ideal target in terms of agr essive expansion spread.
Austria manages to pass 2nd reform, but with reformation coming into play soon and northern Italy leaving the empire it's most likely last reform they'll pass.
Easy wars for the win

This one would be awarding the 'Cold war' achievement as the only casualties on both sides were caused by attrition.
All land taken from Tunis is fed to newly established vassal which will be granted all land with increased coring costs in that region.
Serbia pops out of Venice after they're defeated in a war and with Deus Vult we have instant CB so we put it into use.
Castile is still busy doing Reconquista against Morocco and their allies Portugal and Provence won't honor defensive call due to war exhaustion and loans.
New monarch takes place (somewhere in past decade previous heir died in a hunting accident and thanks to Ottoman government form we got even better replacement). The 5/2/3 kind hearted (-0.05 monthly war exhaustion) is decent replacement to the old 6/4/6 monarch.
Castile is forced to accept 100% warscore peace deal, which includes land connection to Portugal and all provinces somehow bordering France so they can not fabricate claims against Castile and deny us land this way. (Or guarantee Castile as now AI takes actions to slow down player expansion which includes guaranteeing neighboring countries).
France is called in as attack dog against Pope.
Some mandatory stackwipes of Papal alliance forces.
Although Rome was occupied already in 1499 the peace deal was signed two years later to allow some AE to decay in order to have only two countries which are not truce locked with us in the over 50 AE list.
Conquest of Rome provides with sweet +1 missionary which is key factor for one faith and sooner you can get it, the better as there will be always something to convert, especially when you can convert your subject's provinces as well.
To show that even I am doing mistakes



- I saw Great Horde being reduced to OPM with a lot of cores which would make great vassal for usage of reconquest CB willing to accept diplo-vassalization so I immediately married them (was at war with Pope that time so haven't checked alliance acceptance as AI won't accept alliance when the other side is at war) and then I've discovered this

I guess you'll be force vassalized GH.
Sometimes old forts you take from your enemies can you serve one last time before as sometimes the rebels may try to siege mountainous fort.
With Ethiopia as a meatshield Mamluks are attacked for the 3rd time.
While we are already in war with Mamluks Medina is attacked as they're guaranteed by them and their only other ally is Dawasir.
Mamluks are forced to cede Mekka and a coastal corridor towards Yemen in order to open new expansion route.
New expansion routes and opening new fronts should be your number one priority once you're strong enough to bully everyone around.
With fully annexed Medina we now control both of the holy Islamic cities and are already sitting at maximum number of available missionaries.
When you're going for one faith securing all the cities which grant you additional missionary should be one of the highest priorities for you.
Colonialism is born in Portugal and maybe it's a sign for Ottomans to also go colonial
Ramazan is annexed and we should be looking for a new vassal to core land in the Persia region, unfortunately Persia no longer has cores in this region since 1.23 (however if Timmies are beaten badly enough they can serve this purpose).
Age of reformation hits shortly after colonialism and according to the age screen we've already converted 79 provinces (most likely also counts subjects' provinces).
The most OP bonus of this age is definitely -25% warscore cost against other religions followed by the prestige for religious conversions (but we're already sitting at constant 100 due to all conquest of something modifiers).
I am closing to the admin tech 10 which provides 3rd idea group slot and I have two candidates in my mind - admin or exploration. Given the fact that current admin point generation is 14 and with +20% core creation cost reduction it's more than enough to allow almost constant coring and tech/idea progression I am leaning towards exploration (gotta start converting New World as as non Christian nation you can't just take other Christians colonies) which is more fun and it also allows us to expand into much more corners of the World than just by land.
Your thoughts about 3rd idea group slot?