It's hard to give directions for this game, because (almost) every planet has a different name, shield- and materialvalue on a different walkthrough. The one thing that stays the same is the reward.
The rewards for completing each level as it is numbered in the image are:
Hull strength upgrade 2 will unlock Extra addon upgrade 3 Hull strength upgrade 4 will unlock Extra addon upgrade 4
Tipps: - start with the Rail Gun, it is easier to aim with the small and fast ships in the beginning - upon upgrading, choose the Photon Bombs, while you have to get used to the aiming they are far better than your other option
- start upgrading Starting Alloy and Invasion Force Size; the first lets you start of with more ships, the second shortens the duration of each level drastically - upgrade ship weapons depending on what ships you use - you won't need the hull/shield/damage upgrades for your mothership, 2 addon-slots will be enough for some time
- only build the strongest ships as you only have 6 slots - in order to finish the game you are going to need at least the fifth ship (sixth is better)