There are five resources in 0 A.D. : food, wood, metal, stone and population capacity. The latest one being a special one, used only for training units. The last hidden one is time.
They are used for various things, training units, researching technologies, building, phasing up.
DarcReaver wrote an analysis of the resource usage there : http://wildfiregames.com/forum/index.php?showtopic=19889#entry307397
Based upon this, this is how resources could be used.
Resources are split in two categories: basic resources (food and wood) and advanced resources (stone and metal). The basic resources are rather easy to find but are somewhat critical, being used for almost everything (thus, being basic). The advanced ones are more precious, harder to get but required for high quality things. Getting advanced resources is then not mandatory, but having them is a great advantage (or better, lacking them is a strong disadvantage).
Food is rather easy to get. There are multiple sources available, including an infinite one with farms.
From effectiveness, the best is hunting, fishing and gathering from fruit bushes or trees. This is a fast way to get food but it requires to spread more and is depleted at a given time.
Corrals allow to hunt more but is in current state hard to use, requiring to watch the sheep production.
If food is easy to get, it is a critical resource. It is required to train any unit (except mechanical ones). Cutting food supplies is then not that easy to do but it cuts almost everything. The fact women are better at collecting this resource (except for hunting) makes it harder to defend.
Food usage is then deciding which units to train. Having a small food supply allows to focus on other things than creating units, it should then be used almost only for that.
Wood is the second basic resource. It is rather easy to get except on some maps which have only few trees.
Wood is used mainly for building, basic structures requiring mostly wood, advanced ones still a bit (would it be for scaffolding). It is also used for military training.
Wood is in fact used for almost everything, from building to heating, but in different amounts.
Buildings are the most wood consumers. Growing a city, at least on the first phases, should rely heavily on wood.
Metal is either raw metal or used as currency. It is mostly used for advanced topics and mercenaries.
Heavy units then requires some metal, as traders and some technologies.
Stone is the strong building material. Used for heavy defenses and advanced buildings. Some civilizations can then have no use at all of stone in early game while other trade wood for stone on their basic building but with higher quality.
Rushing is a matter of setting up a strong army quickly. It relies then heavily upon food, some wood and a few metal.
Since it doesn't have much wood or using it more for military purpose, the player cannot grow it's city and then phase up.
Turtling is a matter of defense. It requires some food for basic units, a lot of wood for the basic buildings and defenses and then a lot of stone for heavy defenses. Lacking of metal and food, the army won't be that large but defense facilities are there to compensate this.
Booming is a matter of developing very fast. It requires a lot of food to set up a strong economy at start and a lot of wood for growing the city. Then switching to food and metal for advanced units and techs.
Because it focuses on having a strong economy quickly, the player will have a lot of resources of everything, but using wood more for buildings and metal for teching than building an army (at least at first).
Playing with a bit of everything, a player starts focusing on food and wood. The player can create basic units and build quietly, it may requires a small amount of metal for some units but not much.
Having grown its city well enough, it can go to the town phase and have access to advanced units and buildings.
It will require more metal for advanced units and techs but it's not mandatory. Stone will come in play for some advanced buildings and defenses.
Once grown enough, the city phase comes and will require more stone for the latest buildings and a lot of metal for the advanced techs and champions.
The aim is to focus on the basics, quantity over quality. The player will focus on food and wood, and just a little metal. Requiring mostly basic resources, the player won't have any difficulty to find resources spot and almost everywhere is a good spot to be.
Strong on food and wood, the player can train a lot of basic units while still building a lot and cover the map quickly with basic structures.
Being short on metal and stone, it cannot have strong technologies, strong units or advanced buildings (either civic or defensive).
Lacking food and wood, the player will stack stone and metal without really being able to use them. It's a bad choice.
Trying to get most of the technologies and strong defenses will requires more metal and stone. The basic food and wood are still required a lot. Getting less food will reduce population growth, trading some wood for metal will hinder building but have better units or if for stone better defenses.