While there are several T2 weapons that make planetary invasions easier, these are rarely avalable in Galactic war campaigns. This means it's very easy for both players to get stuck in a gridlock if you aren't aggressive enough and establish an early foothold. Spamming bombers is a surefire way to prevent the enemy from getting a teliporter up, and without advanced tech there isn't any real way to counter them. If it were somehow easier to micro the orbital lander it might be somehow possible to spam enough anti-air units, but I just don't have the patience, and a locust swarm of bombers wipes my engineers off the map almost as soon as they land. It would be nice if I could spam interplanetary fighters or orbital weapons, but those aren't available to me yet. Either Galactic war should be more generous with tech, or it should avoid throwing multi-planet maps at the player before they have the capacity to preform invasions.
In this case I had T2 vehicles. Absolutely useless. If only there was a mobile flack truck or something I could drop on them.
If you have access to spinners then you're good to go. Mass produce tons of spinners and astraeuses, area load the spinners into the astraeuses, then drop them on the planet you want to invade. The AI will ALWAYS send their air forces to bomb what you've placed on their planet, even if it's purely anti air. They fly into your trap then get destroyed, then you can put down a portal with an orbital fabricator or some fabricators you brought with you. Make sure your ground units are already trying to push through the portal before you connect them.