Go for this mission just after finishing the last one. It is very simple. You have only to drag your robots to the "steal data" field on an enemy planet, then select technology you want to acquire. I recommend heavy factories or Marauder cruisers.
Now build your new structures - at least two Officer Academies and (when you'll have them) some heavy vehicle factories. Upgrade your stations on Aleraan and Dantooine. Now you can build some Nebulon frigates. Remember to move Mon Mothma to the system in which you are planning to build expensive units. She cuts the costs significantly.
Soon you should have at least one officer and one field commander in your army. Robots are probably done by now, so send them to snatch another technology. From now on it will be your main (and only) way to advance, so steal enemy information whenever it is possible.
Now look at newly activated planets in lover part of the map. Capture them as soon, as you'll have Nebulons, Marauders, artillery and commanders. Be sure to control all available systems before going for next mission, because soon you will get even more planets to conquer.
It is best to capture Bothawui first. Leave small garrison there and head for pirate Nal Hutta system. Then you should take over Ryloth (you will finish trade route this way and receive additional credits), Shola and Mon Calamari. Build important structures on every of these planets. Be sure to have largest available stations in orbits of Kuat and Mon Calamari - you will need them to build heavy rebel cruisers. Build a cantina on Ryloth - smugglers will help your economy.
By now you should have many credits and large army. Conquering Genosis and Tatooine should be easy, and once you finish - go for Kashyyk mission.