I just won this scenario, so I can give some help.
1º - Try to get the better planets as fast as you can before your useless allies get them. There is one planet near Teth which is great for building.
2º Build four freighters and trade with the most distant allied planet. Money is good.
3º Use the bigger planets (9 or more) to build factories and starports and some support structures (not many) so you can crank out lots of ships. The smaller planets are useful for say, making A LOT of research facilities or markets. If you get events that give a bonus to that planet (like the one where you can dump some guys into the sea and get more research), build something that make the bonus even bigger.
4º You begin with a lot of money, use that to your advantage. Buy all the improvements you need, mainly factories.
5º Leave at least one armed ship in each planet incase Dreadlords try to take them with a single transport or more. They don't arm their transporters. But IF those transporters manage to take a planet, it's going to be hard to get 'em back.
6º Force though numbers. Dreadlord ships have SUPER weapons and one of their ships has more firepower than all your fleet combined. Their weakness is their numbers. Their first REAL battle ship takes a hell lot of a time to build, so use that to your advantage. Never fight a dreadlord ship with only one fleet.
7º The weakness of the Dreadlords is that they require absurd infraesctructure to build their ships. So they take a while to make a army. Try to deny them the hability of having more than two ships for combat.
8º BE FAST.
9º Your allies suck. Get only technology from them. Don't let them steal good planets.
10º Dreadlords are demi-gods, so atack Teth with a ARMY of transporters. They will have to DIE. My atack took only one transporter because I gas-ed them. USE these special atacks on Teth, you don't need it alive and well, you need it to be yours.
