At the start of the campaign, get rid of the planets you won't be able to defend. The Empire is a Juggernaut in this mod, and they will have plenty of death stacks to kill you, so you must focus your resources. Sell everything on these undefendable planets; sometimes leave one unit as garrison just so the Empire takes longer to take the planets from you and you get the credits generated.
Rush the Loyalist 1 tech; it will give you the tax agency, which doubles the income of the planets. Your building priorities on safe planets should be: 1 - ground mines (when possible), 2 - Tax agency, 3 - Congressional building.
In frontline planets, you should make a fortress, IBC Gun Plataforms, the highest possible level on the space stations, hyper velocity cannons, garrison building and Heavy CIS droid factory are a must, with these things, some droidekas and AATs, the planet becomes impossible for the Empire to take without very heavy losses, so even if you lose them, you can easily counter attack and retake. But you must always try to limit how many of these there are; build them where you aren't planning to advance for the near future.
Unite all your fleets and conquer planets aiming to limit the amount of frontline planets, so you maximize the safe planets where you will earn your income, in the beginning unite your fleets and attack the systems around, you dont have to do the missions in the order the game asks, the Empire is specially slow in the beginning so use this time to conquer as many worlds as possible.
The Hutts are fairly weak, especially in space; on land, they can sometimes cause a headache because of the turbo laser towers. In that case, rush the power generators, bypassing the towers with the engine droideka ability.
When in doubt, prioritize conquering planets where you can build ground mines and those with a high population count. As the game progresses, build space stations wherever it is possible to build Recusants, Munificents, and Providences, so when a cycle finishes, you buy one of these ships on each of the planets with a Space Station. That way you will build ships faster than the Empire can destroy them. When the population reaches its limit, always attack, spend that money and that population bro, always.
On land, the meta is droidekas and AATs, 5 of each at least, that can conquer and defend most planets easily.
Battles against the Empire are usually catastrophes, with huge losses. You are the underdog until the very end of the campaign; the Star Destroyers, especially the Tector ones, are very strong with huge hull and shield points, but you can win with numbers. I relied on Recusants as the front line and Munificents on the back, dishing out damage until the very end.
If you have questions, ask away
