^The trick is to hold off on doing the "priority" research projects until you're ready for the next story mission to unlock.
You also need to be pretty aggressive with your base expansion early on to get enough satellites in the air ASAP. You should always have at least one satellite on the build, if not more. They take 20 days to construct, so if you need one in a hurry you'll find yourself up a certain creek, sans paddle. Another thing to remember is that you're not really supposed to be able to get *all* the new equipment. You're supposed to choose what you think you need the most and prioritise accordingly.
Personally (I'm still on my 1st playthrough btw) I only made about 4 or 5 laser rifles and two or three laser pistol. Didn't bother with the other laser based weapons and went straight to plasma, which was a huge saving in resources. Thist was possible early on as I was capturing as many aliens as possible and stockpiling their dropped weapons.