I use this piece of software:
Back in its day it was easily the most sophisticated build/sell tool available. Today, it still makes me competitive (or at least acceptably profitable) for a soloist.
The author left Eve nearly 17 months ago but left the code on GitHub. With the help of a friend, I was able to get it running locally. It has not been updated to use EC’s (and I don’t have the programming skill to do so.)
This means I build in NPC, sell in major trade hub, and buy offshore. Even so, since August 2016 my net profit margin is 18.92% building and selling only T1 items. Is that margin the best available? Almost certainly not but the simplicity of my operation is stunning.
Each day I know exactly what to build and what to sell it for based on net profit AND movement. Likewise, its “materials report” tells me each day how many materials to buy (and what price to pay) to keep my raw materials inventory at nearly perfect levels. Its “Market Research” report shows me what I might consider adding to my line of products.
The tool by SJ Astralana is a programmatic work of art.
If you know C#, .NET, and SQL, it could be worth your time.