I research mk2 military as soon as I've got my first planet, and then within the next couple of planets I'll unlock mk3 military and upgrade all my command stations to mk3. I'll unlock mk2 econ a little further down the line, and mk3 econ much later. Once my empire gets substantial I'll start tossing down some mark 1 logistics on some of my main transit paths, leaving military command stations on my borders and econs scattered around.
Depending on how hard you're finding the game, try to have at least 1 mk3 military on every entry path leading back to your command station so that you have some nice defensible locations if you have nasty waves coming in. Leave one mk3 military command station unbuilt if possible so that you can build it on any planet that's getting hit with a counterwave, the 2x muniboost for all your ships is super helpful against waves that are usually one, if not two, marks above what you've been dealing with for the game is extremely helpful.
If you're playing against an enemy with cloakers (especially stealth master/shadow master), the mk3 military stations on your borders are probably doubly necessary.