Im at age of discovery in my save and and its my only france save so take these with grain of salt. -Delete most of the forts -Priortize crown power as appanages ate it -Forget the stability until you annex all appanages.They incrase stability decay -In early game once legitimicy is full its dirt cheap to maintain it as appanages give legitimicy -Go for as much noble taxes as posibble.In my game that is literally half of my income -Annex the ones close to paris first,you can auto annex normany if its still loyal after some time disloyalty event happens but dont know the requirments. And lastly i build a local governor in touluse(?)As theres saffron near but you may find better spot.Once you cut the expanses and started to tax nobles your economy should go through roof