Try to avoid taking a loan, but do so if you must. Use every ducat you have and create a mostly, if not entirely, Cavalry army. The difference is, however, that forty of these units are in Anatolia, the remaining twenty in Europe. The Ottoman Empire, on the other hand, has sixty units.
You have twenty units, all in Thrace (where else?). In order to resurrect this empire at death's door, we must strike a quick, decisive, and most importantly early blow to the Turkish scourge, the Ottoman Empire. However, a skilled player can bring this great nation back from the brink and back on to the world stage very quickly, if said player takes advantage of the early game situation as much as possible. It controls only the provinces of Thrace and Morea (In the AGCEEP, Morea is a vassal, making Byzantium a one-province minor), and has barely an army to speak of. The Byzantine Empire of 1419 is an oxymoron, by that I mean it isn't an empire.
The Early Game: 1419-1550 The Wars of Reconquest The First Ottoman War