Blizzard is shitting on the servers. What's new right?
Remember back in the WoW days where server matainence would extend all day, servers would lag like hell, and there was no reason to be playing, but we all played anyway?
That's how i feel right now with SC2.
Make sure you are always pumping your mineral line. Your max amount of probes that can harvest is 24, so 3 lines of SCV/DRONES/PROBES
Even if you have enough, if you have the extra money, why not build more. It makes it easier when it's time to expand, just grab a chunk of them and go!