As the huns you really want to spark the "great push" of migrating hordes towards ERE and WRE. I horde the Roxolani first since they, sometimes, go east/ south towards the ERE backdoor or even the Sassanids, he he! Then I hit the Sarmatians, who always goes for Constantiople, the the Goths who goes for Rome. The Vandals usually puts pressure either on the Sarmatians and Goths or moves into central Europe moving down the Poo-valley towards their target Cordoba.
When the Sarmatians settle in Constantiople I evict them to sending them towards WRE too. Sometimes though they stay and want to re-take Constantinople. The problem with hordes is that they always migrate west. In one game as the Huns I never settled but sacked every settlement in eastern Europe, the steppes, the Balkans (but didn´t touch WRE or ERE) and it´s still rebel controlled. All factions are now fighting for France, Germany and Italy. So now I´m thinking of moving down the Kaukasus to give the Sassanids a run for their money.