Dude you should go for Bothawai it doesn't start out with much early game and it's a great place to fortify cause it will give you intel on most of the core and some of the intersections Corellia and Kuat plus the Bothans are loyal to the rebellion and when you become the new Republic you can build Bothan Assault Cruisers they're which are good ships with the assault ability which is like boost power to weapons without any down sides also Abregado would also be a good place to take since the locals are also friendly towards the Rebellion and if you have to defend o the ground you can use a abandon heavy vehicle factory which will give you 5 AT-AP's to use in the battle which at this point are decent vehicles for a free spawn.
Also I don't know but if I remember if you want the Mandator you might have to take the space of the planet or it might not spawn but the thing is Kuat starts out with a Hypervelocity gun which is really powerful while Corellia seems to be lightly defended besides the medium shipyard they have in space and I think if you take Corellia or other worlds in the core you'll get a Corellian Battlecruiser and a Corellian destroyer and speaking of which you can actually build those on Corellia once you have the space over the planet and the free spawns they give you for defence are fairly strong they've helped saved my butt when the Empire send a few ships including one of the Allegiance spawns they got when I took Balmorra I'd personally advise taking Kuat before starting a ground battle on Ballmora and Aagau since the free spawns they get when you take those two worlds plus the HV would be almost impossible to take plus the Mandator really can make the difference when going up against ships like the Allegene which looks like it has more hardpoints then the Executor that the Empire get's when they take Hoth.
Also be warned when I was playing as the rebellion when I took Aagau or Balmorra I noticed the Empire got 3 Allegiance battlecruisers, 3 Hawodor star destroyers(excuse my spelling) ,3 heavy Corellian Corvettes and some corellian battleships and destroyers however for taking Coruscant and Aagau you get 10,000 credits each and if you take Kuat You'll get a Mandator type dreadnaught kind of like the one the Republic get in Republic at war.
Aww I also noticed you weren't playing on "Equal Footing" cause you could of got infantry for cheaper on Kamino like field commander and infiltrators who are some of the best units you get as the Rebellion and when you became the new Republic you would of been able to build Mon Calamari, and Sullistan soldiers there for cheaper.
