If there is a troop you really want in the market (like Knights Templar) and it doesn't appear, then just save and quit, and when you enter the game again, different troops will appear in the market. Keep on doing this until your chosen troop appears.
Train something in a castle. Then save and quit, then enter the game again. Go to the same castle and go on a different spot; you will be able to train another troop. Great if wanting to train lots of good troops quickly, stops after all 4 spaces on the castle are used up.
An easy way to get empire points is to set up a empire map match on Archipelago small with three hard Attilas. Then put two of them on your team and fight the other one. Each battle earns you 50 points and they take about 5 min to complete. Profet of Regret