Can someone give me a guide to fighting?

Every game I try seems to go exactly the same way. At some point after building up, multiple people I've never heard of declare seperate wars on me at the same time. Both of them will have slightly more men than me each and I don't have enough gold for Mercenaries. I lose both wars/die in battle and reset. Where am I supposed to go from there or win/prepare for these wars in the first place. I click 'call my allies' and they never turn up in time.