Standard for 1.8 strategy:
0. Send diplomat to Austria, build army and fleet, rival Venice and Genoa and hire +dip avisor
1. DoW Albania day and annex
After taking Balkans I was still weak, so I turned my eye to Theodoro, vassalized them, crushed Crimea for Kaffa, vassalized Circassia, fed them all Caucasusian nations and then stomped Ottos.
So, this is a cheese strategy, which is fine, but if you don't do the back in time thing you can't get Albania.
I take Diplo first, almost all the time, even then I am +2 diplo relations. You can RM proactively then to get your family on the thrones of Europe. Look for any of the top countries to show up on the alert. I am constantly at +100 improved relations with Denmark/Austria/Poland/Lithuana/Muscovy/France/Sweden/Novgrarod (if they are doing well)/Castile/England and anyone else significant.
That way when they show up on the list, boom, marriage. Since I am constantly near 100 prestige with good score, my family moves to the front of the heir list and now I have a chance for PU or to claim thrones.
Have you had anything just outright flip to you? I think during war time there must be some event to protect Orthodox provinces. I got a core on Vidia, and Kaffa just flipped to me outright. You have to find some way around Austria to get Genoa, for me that came with an alliance to Venice, two birds with one stone there.
With and without cheese you should have more than enough money to not really need to worry about accepted cultures. I think it will help long term with large conquests to have humanism, but it would never be my first choice, my second choice is religious. Too many free points from missions to convert, good events and easy CBs and other bonuses. I will take a mil idea finally 3rd because I am just building armories like crazy and have had war taxes for every war, and am typically 19 years ahead of time on mil tech, but man, those break points are key.
Humanism...hmmm, maybe after another diplo choice. Did you Westernize?
Would vassalized electors vote for me, especially when they hate me for my aggressive expansion?
Should I be already in HRE for electors could vote for me?
Actually now all colonizers are very strong: I had to murder around 200k (!!!) Portugal's troops to before I could freely besiege their provinces. They have around 250 forcelimit and 900 naval, which means that their max army was around 400k and 1200 (!!!) ships. Take Castile first )))
Thanks for the advice, I will go for Castile, but then I get 3 relations...ouch. Yes, you can easily repair your relations with your vassals, they are no different than force vassalized, you get a big bonus to the voting because they are your vassal, keep in mind that the first vassal doesn't get the AE from taking the second, generally you only need two if you kick the crap out of Austria, but this is the tricky bit, you will need 3 if Austria is intact. You can get these vassals without fighting the Emperor easily enough, just guarantee strategically. Still, the best way is to declare on the Emperor and vassalize every elector they are allied to.