As with most Command & Conquer games, you players have to manage not only units, but also the economy. Compared with PC games there is no power management, but there is population cap.
Tiberium
When the match starts, the commander has 100 Tiberium at their disposal. There is a 10 Tiberium income every 5 seconds[1].
Most maps have Tiberium patches, four patches on each side. To increase the Tiberium income harvesters (costs 60 Tiberium to deploy) can be deployed to said patches. Each harvester provides more Tiberium than the basic income. Initially player can deploy only one harvester, but when they reach level 9, they can deploy up to two harvesters. Harvesters take up population cap like any other unit.
As the battle goes on, the Tiberium from basic income and harvesters increases[1].
When an enemy harvester is killed, the attacker receives 80 Tiberium income. If a harvester has died to a friendly fire, no side gets any Tiberium income. It costs no Tiberium to redeploy a lost harvester.
Nod faction has another Tiberium income source — Scavengers. When a unit dies, it grants 10 tiberium for each friendly Scavenger next to the dying unit[2].
Population cap
When deploying a unit, there is a cooldown on how long until the next unit can be deployed. The more units are there on the battlefield, the longer the cooldown. When a unit dies, the cooldown is reset.[3]
The game interface shows that the population cap is 6 units, but that is a soft cap — more units can be deployed, but the cooldown takes a lot more time.
Although cheap units are usually more cost-efficient than the more expensive ones, population cap makes it difficult to field them in sufficient numbers to counter more powerful units.