Great guide! Just took back all of my cores and with only one loan too.
What would you suggest be the next immediate steps after the first war with the Turks? Would trying to expand into the balkans be a good idea?
It depends on how things are going in your world after the war...aliiances, wars, rivals and stuff for the AI..
I think the following are possibilities or suggestions for next steps:
1) Obviously recover your economy, manpower and build up army and naval forces.
2) Integrate Athens asap
3) Establish any new strategic alliances that work best for you...Austria, Poland, etc.
4) Check what is going on with Crimea, Theodoro and Genoa area. Look for opportunities to expand there. If Theodoro somehow survives you may be able to simply diplo-vassal them later. If going for the achievement you need Cafa.
5) Check Byz Rebels in some of the provinces/islands around you. I had like 2 or 3 provinces flip to me and I supported rebels when I could.
6) Venice and the Knights are obvious targets, Get all the claims you can on them and attack when they are in trouble. Venice may have strong alliances like a France, Aragon or Castille, but I attacked when those allies were burned out in others wars. Plus, Hungary and Austria usually hate Venice so will join that war easily. Get Crete, Corfu, Negroponte, Naxos, (Albania, if Venice grabs it which they usually do), and Rhodes. Dalmatia is one you can get one way or another later on. In my recent game, Bosnia had grabbed it off Venice when I was crushing her. Then I vassaled Bosnia shortly after.
7) Support rebels in Cyprus when you can - it usually has rather high revolt risk for some time. You will likely have to fight Mamluks or possibly Venice for it. If it doesn't flip I would probably wait until after second war with Ottos so you can build up more navy to ice the Mams.
8) I'm big on vassals and Influence. I leverage that as much as possible in games and i think it works here. In the first Otto war, I actually took one Bulgaria province and released them, then fed all their cores back in 2nd war with Ottos..that's quite a lot of the Balkans right there.
9) Serbia and Bosnia are usually ripe for the taking (and Ragusa if it still exists which is unlikely). I usually vassal one and feed the other but that is up to you. I probably would not attack them until you have established a land border via Albania or Bulgaria.
10) Keep fighting and expanding into Anatolia. If any of the Beyliks exist you might vassal one and feed them, but otherwise keep the pressure on the Ottos. Honestly, after that first war, the Ottos were pretty much toast and the wars were fairly easy, although with ally help. After the 2nd war I could handle them on my own.
11) Hungary will likely eventually turn hostile later, especially if you get alliance with Poland. They might attack Wall too, who assume you are allied with. I dishonor call from Wall and let them go, you can easily release and feed them later. If Wall otherwise survives for a long time, you can probably eventually just vassal them when you get large enough. (they have high core cost due to tradition so I'd not fight them unless you fight to vassal them)
12) Later on Itally may be a good target. Keep eye on Castile/Aragon/Naples, etc. You will get mission on Venice as well to end them.
13) I picked up Trebizond easily in a war with Crimea, claiming their vassalage from Crimea. Anything could happend to Treb, but you want that one way or another.
14) Keep tabs on Orthodox Georgia and Circassia. Also a very volatile area so anything could happen to them. Obviously good place to expand religion wise either in a friendly manner or aggressively. Vassal one/feed the other or conquer outright. (in recent game oddly Georgia not only survived being QQ's vassal, eventually gaining back independence, but grew quite large and allied Moscovy. Surprising the same happened to Ryazan, another Orthodox area.)
Once you restore them Empire and take most of Anatolia you will be a very big power.
I like Influence, Admin or Innovative, and Offensive as first ideas. You don't need Religious as Byz unless you just want it for the CB. You don't need to westernize but might try to do so later via Vienna or Prague.