Just finished it, here are few quick tips on how to make it:
1. Claim dagestan and DoW 2PM that possess it, while constantly improving relations with Qara.
2. Vasalize that minor (easy) and gift (+25 relations) Qara , so that you have over +100 relations - that means they won't be hostile towards you anymore
3. Claim Astrakhan and dow Golden Horde (wait for them to go in war against crimea, kazan, etc, which happens very often). Take as many provinces as possible from them - I took 5 in first war and formed Astrakhan as vasal.
4. By now you can integrate 2PM vasal and that gives you access to circasia and georgia (easy targets).
5. After few decades of conquering those teritories you will be very strong and you can basically dow and conquer provinces from Qara. Be sure to rival Qara and improve relations with Otto which will also rival Qara - that makes you viable for allying Otto.
6. Here comes the hard part - once you eat too much teritory Otto will go hostile towards you and they also DoW me. It took me about 10+ years to get white peace somehow - with lot of luck, manuevering troops, etc.
7. After this try to grab few more provinces from nogai,crimea,ryazan, etc.
8. DoW Timurid and be sure to fight Ottos again, since they are 99% allied with Timurids. This will be very hard war (lasted almost 20 years for me), but after 10 years or s9. I peaced Ottos (I released Armenia and some other stuff, but that's irrelevant - important thing is that Ottos are out). Since I was 3 or 4 levels above Timurid in military, it wasn't too hard to beat them in battles, but be aware since they have 3 times your numbers.
10. After lot of battles, sieging, etc I took from them those 5 critical provinces and released Persia. Waited 10years and integrated persia.
11. End
I hope this helps, cheers.