How to manage building an eco and an army?

I'm a noob but play a lot and watch a lot of t90 but have trouble leaving the low 1600 range. I find I either focus on booming but have no military or I focus on military and am way behind in advancing to the next age pretty much sealing my fate. However I feel like others are doing both really well and I can't figure it out. They will be knocking on my door with an army and still advancing faster. I've learned hotkeys and general macro and haven't dabbled to much in build orders but this aspect is really hurting my game.

What helped you to do both and really increase your ability?

Thanks and much love!