I'm not an expert, but my advice if you don't have enough money would be: concentrate on your most profitable provinces, invest money there (on buildings and especially farms and mines in fruitful provinces if you lack money), forget about low-economy provinces, leave them for a while. Try to qonquer rich provinces. And I think everything should be fine. By the way I've got the same problem while playing the Almohads, early age, normal level. So I concentrated on economy, especially gold-mining first (as this investment pays off very quickly and brings much profit), then on farming in beneficial provinces and last on trade (as the navy was set-up). My economy improved very much. Now at the beggining of the campaign, I always concentrate on the economic side of the game (of course there are exceptions). So these are my thoughts. Best of luck in qonquering Europe!