There are a couple of ways.
If you increase the level of your Construction Yard, it will allow you to store more Tiberium, Crystal and Power.
Increasing the CY also allows you to build more base structures - to a maximum of 40.
Two main storage structures.. a lot cheaper than always upgrading the ConYard are Silos and Accumulators.
When you first build a silo, you will be able to store a small amount, perhaps 20 Tiberium and 20 Crystal.
Upgrade the silo to level 2, level 3.. and that storage will increase quickly.
In the same pattern, an accumulator will allow you to store power. Increasing the level will allow you to store more power.
These storage buildings also have another plus - put a silo next to any harvester, and you will increase constant production and enable bonus packages. Put an accumulator next to a power plant, and you also enable bonus packages and increased production.
Increase the levels on those storage buildings, especially if you see that your resource counts are usually in the yellow or in the red.
