Manufacture is blueprint-gated so you've got to get lucky with exploration especially in mod-heavy games where the odds of getting exactly what you want are lower. I'm not too familiar with raiding for blueprints - perhaps you could do it early if specialized and sneaky enough!
Player needs marines; and bringing several Phantoms (or other raider ships) with ground-pounder built-in mods help. Player does not need much if the market does not have a battlestation and/or market is small. Those that have battlestations should have their battlestations disabled before the raid to lower defenses low enough. Big planet with battlestations are meatgrinders.
Also, blueprint drops from raids are random but favor unknown blueprints. Also, every blueprint drop is a singleton, include those normally found in packs. It is a good idea to search for tech and faction packs in salvage found before raiding markets for rare singletons. Also, it is a good idea to raid soft, weak markets first until all of their blueprints are learned, then move on to tougher markets for their exclusive blueprints.
For standard stuff, my blueprint hunt goes in an order something like this:
* Salvage ruins, research stations, and the like for packs (low/mid/high tech, missile pack, pirate/ludd/auxH packs) to get the common stuff.
* Raid New Maxios in Magec. No patrols, small market with no defenses.
* Raid Asher. Small market, patrols hover around Gilead, they rarely get close Asher unless Asher itself is close to Gilead.
* Raid Kapteyn Starworks. Small market, occasional patrols from League neighbors. Get large pirate hulls here.
* Raid Reasvelg. Small market, but frequently guarded by a patrol. Last of the soft targets. Get XIV ships and few weapons here.
* Raid Culann. Medium market with a battlestation, and usually has guards. Easiest of the hard targets, but still harder than above. Raid for high-tech.
* Raid Sindria. Big homeworld with battlestation, and heavily guarded. Alternative for some high-tech otherwise exclusive to Tri-Tachyon.
* Raid Kazeron. About as big and hard as Sindria. Champion is League exclusive; get it here.
If I am lucky, I may find everything by the time I get through with Culann. SIndria and Kazeron are more like last resort if salvage has been unkind (i.e., no Champion).
Chichomoztoc is the hardest target, but there is no need to raid it for blueprints since Reasvelg in Valhalla is a much softer and easier target. Only reason to raid the Hegemony homeworld is for the pristine nanoforge.
And of course, historian for Legion XIV (only way to get that one), and flashy pirate for Phantom and Revenant blueprints if those two were not found in salvage.