Patience can be a virtue. Wait and see what moves your enemy makes then be aggressive.

Don't be afraid to reinforce towers if you need to. Defensive towers function just like regular base so having a strong one early on the map is in your interest.

If the enemy just upgrade one of their lower end bases it means that the base has little to no defense, and it's a prime target for you.

And if the enemy just tried to take over a neutral tower good odds are that he now has very few units left after having to deal with conquering tower. It might be a good time to attack.