I organize the way I do, because there are two kind of opponents.
Pirate bases (of the normal kind), pirate ships, enemy strike fleet, various bases not being defensive or spaceport. You need a fleet to handle these. Only the AI uses a 17 ship fleet to kill a mining base. Or me trying to draw forces away, or having slacked in deployment. A 4 destroyer fleet should be able to defeat all of the above, if they don't add something more power. Raider is a name, the AI call them strike.
Then there are "the rest". Medium and larger spaceports, the larger AI fleets. You need to be able to beat them. I call mine battle fleets to be able to sort and find them. They should kill a Large Spaceport, or an enemy main fleet. But not both at the same time. When LSP + 4 bases start showing up, I either use 2 battle fleets or make a couple of extra large ones.
Unforeseen plays a different game than me. He roleplays more and has fun doing that. I make things simple and with force. And have this thing about not automating ships, so my smaller fleet have to do all the pirate defense there is.
One thing to realize about this game is that there are many playing styles. Some are addicted to ship design, and making sure to have the perfect ship for every job. Others enjoy fast paced game of war. Other loves the slow grinding games. Everyone is different, and any style is fine. Which makes it a tad hard to make recommendations on what to do...