How can I get better at the game?

Feel like I'm hitting a plateau. My biggest problems are defending large early rushes, and late game imperial armies where it always seems like my opponent has a larger/stronger armies and more trebs. Defending the scout rush is tough for me because even if I get/have pikes up they just move to a different part of the base. Should I set them up to defend wood line and gold? Sometimes they just pick off farms.

Do I need to focus more on pushing my economy towards specific units and get more of them up?