Some random ideas, I have not played for quite a while...
- Pirate hunt. Spying seems work intensive and slow. I would focus on long range scanners to see their travel lines. I know their base is on a fuel source. If their course is towards my colony/mine whatever, the other end is probably at a base. How many fuel sources with nothing on them are there in that area? Send single ships to each of them, and consider queue "refuel" or whatever to avoid them getting into a losing fight. When I got it somewhat under control, I know that they need fuel sources, so I build on every single one I can get hold of.
- Hurting stuff? I never bothered with manual designs, but if a fleet of 20 does not work, bring two fleets. Or more.
- In troops part of colony interface, you can set troops as garrisoned, those won't get picked up. I use manual ships, but automate single unfleeted transports since they are good at filling up as troops are available. I make sure to garrison some on conquest (and full transports are added to troop fleets and of course not automated anymore).
- Defense? 1-2 troops for the non-valuable colonies (that are most of them). 10 or so to stop a small drop on the valuable ones, but the important part here is spaceport, defensive bases, manual defensive fleet, to make sure the only possible accident is a single transport drop that is handled on ground.
- Expansion? Careful at the start (helps with pirates too), grabbing territory (good colony prospects) as priority.
- Fuel? If you build on all sources, that won't help. If your capital has few nearby sources, don't use that as your construction site. I do not know your pace of game, I am kind of slow, and will only ever have local fuel issues. And I love resupply ships, and those can live on top of mines and help out in a region with few fuel sources. I would look at the gas mines around your capital, if they are full of fuel, it is a transport issue, if not, it is a (local) fuel issue. Things that will help with making local fuel shortage at shipyard are extra large fuel tanks, and losing ships (which means that more are built).
- Aggressive races? I have not had much issues with those, which may be luck or doing the right thing. Colonies are either, rich, medium, or poor. Most are poor. So do not focus a lot on grabbing those, or keeping them. I usually try to keep my borders clean, so I grab them to achieve that. So, to fund their war, they need the rich colonies, and they will help you in defense as well. The rich border colony (that you grabbed is lovely, you can defend it well and waste their fleets as they try to take it.
- How to abuse the AI in war? Know that they usually attack the closest colonies, so do not focus defense on those "away" from the front. With a proper blob of a territory, only the border colonies are exposed. Make sure your fleets are stronger than the AI fleets...
- During a war that you want to end, look at "negotiate a deal". Check the price for peace. If the AI feels it is winning, the price is high, if the AI is losing the price is low. If it wins fights, grabs colonies it feels it is winning, and vice versa. So if I want to end a war, I check the price. If low, I buy it. If high, I focus on busting some mines, wreck a fleet, take down a spaceport... And check again, the price is probably low, and I can end the war.
- Oh, and if the AI has a colony with a lot of troops, leave it alone (if you want it). Notice your AI emptying worlds of troops, the AI does that too. When the troops are gone, you can take it.
- As written, I try to have a blob of territory. If an enemy gets colonies on both sides of my blob, a priority during war is to get rid of the "outliers" of my enemy so that I know for sure which direction they attack from. So apart from a few "oh, ****" fleets around the empire (in case I get jumped), the area the AI attacks from should be known and I focus there. I have long range scanner coverage to warn me of attacks. I have only a few important border colonies, that I will micro manage if attacked (target troop carriers first).
- My tools.
- My main battle fleets, of maybe 15 AI designed cruises and 4-5 carriers (I rarely play until capitals as research is always slow). They should be able to bust any AI fleet, and also take down small and medium spaceports. And they can sit on colonies in defense.
- I have some larger fleets, of maybe 25 cruisers and 10 carriers (or whatever). I call them Crusher fleets. They should manage a large spaceport (and a defensive base?). One can of course also use two main battle fleets, two crusher fleets, or whatever it takes if you have a really strong target.
- I have one or more transport fleets with a non-troop carrier leader, attacks are done with single transport orders from these fleets (it makes them return to leader after dropping their load). (Giving such a fleet a "load troops" order is lovely, non full transports head out and return to leader after loading once).
So if I am somewhat prepared, the start of the war goes like: Fleets head for enemy systems (but defenders are left at valuable, front line colonies), crusher fleets attacks spaceports (large ones). Transport fleets are parked in safe (empty) systems near the front line. Fleets will blockade after fighting ends (keeps them at the colony). Behind the attackers, single transports are given invasion orders, they should arrive when defenses are down (and there should always be enough to win). I use some smaller fleets to attack the weak colonies, maybe 6 destroyers or whatever. Mostly to distract any locals while the transport drops its load. No need to use a main battle fleet on a fresh colony...)
If all goes well, I will maybe have busted 2 important spaceports, wrecked a few enemy fleets (in defense, or in enemy systems). I may have conquered 4-5 small colonies and battle rages towards victory in the (former) spaceport colonies. Set garrisons (single troops), automate or "load troops" with now empty transports, after a little while move defensive fleets forwards (as former border is no longer border). Maybe send in some resupply ships to fuel crusher fleets traveling inside enemy territory wrecking spaceports. And decide if you want to run "step 2, step 3" or just end the war. The enemy should be happy to end it after losing every fight (and 5-7 colonies). I feel that the opening punch is of course the best, as transports are full, and battle fleet should not sit in newly conquered systems to bust enemy ships that arrive with outdated orders (like move or refuel).
And in an early war, grabbing a valuable colony (but I stay away from the capital) is still key. Or just hurting them enough to end it. Blockading the capital is fun, though.
I usually play this way, and enjoy having just manual diplomacy, manual military ship building and operation/fleets. And I use the buttons beneath selection panel to queue fuel mines.