if you really want to make isk in industry you basically have two main options.
Either focus on manufacturing just a few products at high efficiency with high trade volumes and small but reliable margins. You make for the small margins by mass producing them.
Your other main option is diversify. rather than just manufacture try to cover as many steps in the ore >>> final product process yourself.
To maximise profits you need to find the best method to accomplish each step. Some skill with spreadsheets comes in really handy here.
Step 1 mining the ore
personally I do not recommend doing this step yourself. mining takes a lot of time with a poor isk per hour return. It is also very difficult to mine enough ore yourself to sustain even a modest manufacturing portfolio. But if you enjoy mining, your ore has to come from somewhere. just remember to count the ore you mine at market value. If you can sell the ore for more isk than the products you make from it, you are actually losing potential profits. Ore and minerals can generally be found much cheaper the further you are from a trade hub. however trade hubs see a lot more volume. what is best for you goes back to the first decision. High volumes at low profit or Higher profits at lower volumes.
Step 2 processing the ore
buying raw ore and processing it yourself can be cheaper than buying the minerals from the market. these margins can be just as tight. you will need maxed skills and access to a decent refinery for this step to be worth the effort. Again, buying ore or minerals can be cheaper further from a trade hub, but high volumes of ore can be hard to find.
Step 3 Locating your Home Base
Location is a huge factor affecting industrial profits. there are 3 basic locations you need to balance. the source for your raw materials, your Home Base where you will do your manufacturing, and where you sell your finished product. generally the best place to sell products is at a trade hub. As said before there is an abundance of raw materials available here, However this is usually the most expensive place to buy those raw materials. How far are you willing to go? Cheaper raw materials increases your profits but adds to the hauling or Logistics you need to handle. do you locate your Home Base close to your raw materials, Closer to your selling point, or somewhere in between.
Step 4 Logistics
Logistics is a big issue to deal with. you have a few option.
Keep every thing local. This will drop profits but you will have no logistics to deal with.
Pay someone to haul raw materials to and finished products from your Home Base. This will cut into your profits but can save you a lot of time.
Or you can Haul it all yourself. This can maximise your profits but can be very time consuming to deal with. Not to mention the risk factor of a hauler getting caught by pirates.
Step 5 Complexity of your Operation
You next have to decide how complex your manufacturing operation will be. There is a wide range here. from one step T1 to several steps in T2 or T3 manufacturing. The more complex the item the more profits are available, but just like other steps in manufacturing some of the profits are attached to each stage of the process.
Overview
They key to remember is profits are attached to each step. The more steps you do yourself the more of the profits go into your pocket. however if you lack the skills it may be cheaper to let someone else do it.
-There is profit to be made in logistics moving raw materials from remote locations to your home base or trade hub.
-There is potential profit in refining/reacting ore, moon goo, T3 raw materials into useable minerals or other materials.
-You can increase profits by locating your home in a system with a low industrial index, and/or an Engineering Complex set up for your type of manufacturing.
- low profit margins can be offset through high volume. making 1% on items you can mass produce and sell as fast as you can make them can give you more isk per hour than an item you make 10% on but sits on the market for weeks before it sells.
-The isk you pay someone else to haul your loads can go into your own pocket if you have the time and skills to fly a freighter to collet raw materials and deliver products to market.
-Finally if you are manufacturing T2 ships for example. there is reactions turning raw moon mats into processed moon materials. then those materials are used to make components that are then used to make the ships. If you are 0nly doing the final stage then someone else is making profits off the other stages.
How do you choose to make your first billion isk as an industrialist? 1% profit on 100 billion isk worth of products sourced, manufactured, and sold locally, 10% profit on 10 billion isk worth of products with significantly more logistics involved. Or somewhere in-between. The profits are there, You just Need to do the research and put in the work. you can find your niche.
I was buying ores and refining them and getting minerals cheaper than i could get on the market this gave me an edge, i didnt have to mass produce and could still make money that was worth the effort. But now the margins are really thin after the Lifeblood expansion. So im not happy about that, especially because i invested alot of skillpoints into refinery effeciency of ores 
Shame on CCP