If You are new to Ara may be shocked why the classic 4x Strategy "More is always better" it will have painful consequences even on easiest level.
It may seem brutal but it is actually the hidden gem of this game which make it more difficult but also far more rewarding and above all more realistic.
The key of success consist not in raw greedy amassing huge amounts of all kind of resources but in wise chose priorities.
It make no difference if your city produce +1 or +1000 food but is huge difference between -1 and +1 - it will be like hell and heaven. Both the Good and the Devil are hidden in details.
Sure the extra food/money/iron will go in the national reserve which is always nice to have but always you need to focus all limited slots/goods to spot where it make a real impact in results.

Each city have 5 quality of life indicators which are crucial for your success.
Happiness is as always the most important but anything beyond 100 is a waste and you should use your wine or painting somewhere else where is badly needed.
Happiness impact a lot all sorts of production including food. You always must try to keep it 100%. 99% may result in huge trouble completely halt of population grow if food become negative.
Health it s also important because it will give the actual grow rate of your minions.
But if food is negative your city health become completely irrelevant because it the grow will halt.
For small city is important to have good health because it will make it useful in shorter time. If your city grow overcrowded then it will be far better to use amenities slots for some other more useful stats.
As always more research is always welcome but having education beyond 100 will not provide any benefit and you must take extra books and candle to somewhere else where may be useful.
You will notice is no difference between 41 and 59 value for any indicators. Always it is important to focus on improve the extremes +1 is much better than 0 and 100 is much better than 99.
Prosperity work in same way like Education but on easy levels gold will not be a big issue. Rushing building is expensive and most be used only in critical situations like training soldiers or walls if enemy may be close.
Security is important only on cities which DEPLOY armies otherwise I keep it 0 if border is far away saving slots for something more useful.
I use usually a single city with manned walls where I deploy all armies if is possible. Unfortunately in game is never display the home city for armies - as workaround I rename each army as soon as deployed like "Baghdad rifles" in order to be able to track it latter. In peacetime if I feel safe I reform all green armies detach them from home city in order to save security stats and in case of trouble I will redeploy on border cities where is expected to have higher security levels.
I hope you will use my tricks to have a better Ara experience. Actually finding the most suitable strategy is the whole fun in 4X games. I think the game have a undeserved low rate in steam probably due incomplete manual and poor wiki available at this moment.