Here's some small handy tips that might make things a little easier for players struggling with the campaign.
Don't just mine every system you get, when an invasion starts somewhere, and you place mines then, it will actually push the evasion back 1 turn. This means that in some cases, a good fleet can move from invasion to invasion.
In battles, alt allows you to see the size of debris fields and those cloudy things and the health of fighters... But if you double press alt, it will simply turn this option on, so you won't have to hold it.
Some regions have systems that aren't accessible before you pay Battleplans to open up the paths, this can be expensive if you don't have a steady income of Battleplans, meaning it might not always be worth it... Some systems are VERY worth it though, like in Nemesis Tessera for the Imperial campaign, it has the Obsidian Depths with a planet, that once upgraded, stops almost all invasions, meaning it's one less system you have to keep a close eye on.
Sometimes, in systems you only have a small foothold in, but aren't necessary for your current top mission, you will find systems with a lot of enemies. If the systems aren't critical to obtain and the benefit of obtaining them isn't that high, it might be better to let these enemy factions simply duke it out with eachother. You can always come back later and take control when they've weakened themselves.
And that's it for now!