In my opinion, ballistas can only be effectively used for defending a castle and during a systematic advance against the enemy. Due to their slowness, you can easily fall behind in development compared to your opponent, and stockpiling them in your castle is simply not worthwhile if you don't use them. It's better to build spearmen (excellent warriors with a superior ability) for normal development, and hire ballistas in a separate building, or in a second town (although it's more advantageous to build spearmen there if you're already building them in the first town). And I consider the golden golem to be the best fighter. It has a very high amount of health at level two and excellent stats. It can be used (and should be) as cover for djinn (although the opposite is also possible: take mages at level two - they are good with their spellbook, but they are very fragile, and as cover - and not only as cover - for example, with teleport and blessings, send them into the enemy's territory).