Last week I bought the supplies to make 110 Invulnerability Field IIs which is not too hard. Minerals for the invulerability field Is that make up the base of the tech II item, advanced moon materials for the shield emitters, a few industrial goods, and bam! I'm done.
This week I need to buy suppliers for building 4 Hawks (Assault Frigates) and 10 Covert Op Cloaking Devices. This requires a lot more ship components to be built than the invul fields, so I needed quite a bit more advanced moon materials. Not a big deal... until I couldn't find any Fermionic Condensates. Not in Hiematar, Metropolis, or Molden Heath regions.
Well, I wasn't about to travel to Jita for one material, so I checked my spreadsheets and saw I needed that material for only one component for the Hawks so I simply went on the market and bought the components directly instead of building them myself. More expensive but it allowed me to get all the Hawks into the factories this morning and should be ready tonight.
For those not familiar with Eve's manufacturing (aka crafting), here is a diagram that explains it.
At the simplest, manufacturing involves taking minerals from asteroids and putting them with a blueprint into a factory to produce Tech 1 items (top left circle and top middle rectangle) which you can then use or sell. Anyone and their dog can do it pretty much without any training.
Tech 2 production is a lot more involved and hence the rest of the diagram. Not only do you need minerals from asteroids, you need the Tech 1 item (quick explanation: almost all Tech 1 items have Tech 2 version which doing the same thing as the tech 1 version only much better), industrial goods that you buy from NPCs, Ship Components, and the blueprint for the tech II item.
The ship components themselves are built from blueprints and advanced moon materials. The advanced moon materials have to be created (in a reaction) from processed moon materials, which are created from raw moon materials, which are mined by player starbases from moons.
My operation buys the minerals and advanced moon materials from the market, leaving the mining, refining, and reaction-ing to other players.
Of course, this totally ignores the blueprint research side of things, and the skills required for ship component and tech II construction which varies depending on the item.