Oil is power
Controlling more derricks than your oponent is always better. Keep an eye on your power generators to be sure there are enough of them for all derricks to work. When a derrick is not bound to a power generator, it's arm stays still.
Building a power module on a power generator will increase a lot your energy production, but it will require two construction trucks to constantly repair the generator. While the module is in construction, the generator is not producing energy. Make sure you have enough energy before building the module not to waste time waiting for energy before starting the construction. It is a good idea to start producing the module when an other generator is available and when you have more than two trucks to still be able to start emergency constructions.
When you don't have the military advantage, you may try to gain time by attacking derricks or trucks repairing a generator to harm your oponent's production while you adapt yours.
Keep your energy low
While gathering a lot of oil is good, stockpiling energy is a waste. You should be constantly producing, building or researching to keep your energy bar low. If your energy keeps increasing, build more production facilities turn the overflow into something usefull. On the contrary, if your energy is constantly negative, some of your facilities were produced too early and are not usefull at that time. It may turn against you if your oponent used the same amount of energy you spent into the facilities into a striking force for example.
Keep your units busy
Every unit was built on purpose. Some tanks sitting at the base could be usefull in case of a sudden attack, but there are often other and better ways to use them. You will be attacked if you don't put enough pressure on your opponent. If you have enough map control, you will know when and where an attack will happen and you can use only the right amount of defenses. Of course, your opponent will try to do the same.
Attack, defend, expand
These three tactics compose the base of a rock-paper-scisors. If your opponent is attacking, defend. If your opponent is defending, expand (that is, take some derricks and build structures). And if your opponent is expanding, attack. This apply considering each players are doing well regarding resources management. If you spot your opponent expanding and attack while having a thousand of enery in spare, your army could still have the same value as your opponent's and lose the fight anyway.
If your opponent is attacking, you should defend not to lose the game instantly. This is a tricky situation if you don't have an advantage. If you see that a raid or a rush is being prepared, stop expanding and use your construction power to add a few defenses to assist your tanks. This will either turn the battle into your favour, or prevent the battle at all. In both cases, your opponent has produced units that cannot be used safely yet.
While your opponent is defending, you should be able to gain some map control by keeping the pressure on your opponent's side. This leaves you more space to expand. If you opponent is forced to turtle, you'll be free to gain more power and take the advantage on the long term.
If your oppoment is expanding more than you are, you should have more units or better ones because derricks are not free. You will have a short time window where you should have an army advantage. If you are swift enough you will be able to deny expansions. Even if you are a little behind, taking down a few derricks or some construction trucks take away some precious energy that will not be spend into an army.
Know your ennemy
When a group of tanks reaches your base, it is generally too late to react or adapt. Guessing what will come the sooner as possible allows you to either adapt to what is coming or take action to prevent it from happening.
Scouts are cheap and fast. These tanks or VTOLs will provide crucial informations about what is happening, which may be more valuable than the poor damage they can inflict. The more you see, the more you can predict. Having more map knowledge and control allows you to have more time to react while givin less room to your oponent to surprise you, as well as generally more energy income.
If the composition of your army makes it better than your oponent's, try to crush it with little losts. If it is not the case, try to find a way to deal damages without exposing your units too much or at places where your composition is better.
For example strong units are often slow, or in limited number. If your tanks are lighter, the result of a battle will probably be in your defavour. But you have more splitting and hit'n run opportunities. Fast units are generally not very effective against defensive structures. VTOLs can be attacked only from air or with dedicated AA turrets. But when a VTOL lands, it takes more damage than regular.
Structures and height can also provide cover from direct fire, giving oportunities for evasion or indirect fire barrage.