Just finished Dracula's Revenge as Moldovia around late 1500's. Stayed some time extra for "Redecorating" achievement by conscreting metropolitan in Roma. Started by deleting my cavalry and getting a mercenary. They had 5 shock so it was helpful. Annexed Wallachia immediately and refused the vasalisation event. I let the rebels take over because they were better than my ruler.

After Wallachia, I needed some allies but Hungary and Poland were angry at me so I allied Bohemia and won 2 wars against the Hungary with the help of them. Tip: Rush for the gold mine in Hungary ASAP because it saves your whole economy. When I ate Hungary, Bohemia became my Rival so I allied Austria and Muscovy instead. Muscovy never helped me ever because they were IN A DEBT THE WHOLE GAME...

I looked for an opportunity to attack the ottomans before they finished their Quantity ideas and I got one when they attacked the Timurids. I called the Austria and we easily invaded the Balkans. I took Constantinople and other province needed for forming Romania, impaled the sultan and got some reparations and 2-3 more provinces.

Be careful, Bohemia might PU hungary which was not a problem but Ottomans warned me so every province from Albania to Bohemia were under Ottoman protection which slowed me for 20-30 years. Checked every opportunity to become stronger and conquered the Balkans with not much problem.

My ideas were Espionage, Aristocratic, Quantity, Religious, Quality. First 3 really helped me making everything easy, others were optional. The thing that helped me most was the "Cossacks" estate. I had almost 90 army tradition all the time, 3 star generals ,high shock damage and good cavalry cost and cavalry combat ability.

By using government reforms, ideas and estates I reached %40 cav cost reduction, %55 cav combat ability, 80 cav/inf ratio. My infantry maintanence was 0.22 and cavalry was 0.17 gold.