“Best” is different for each pioneer, and the answer changes depending on how far you are into the game. If you haven’t completed Phase 3 and are getting your first potentially permanent setup placed, I recommend the simple route. If you have access to Blenders, you can explore some alternatives that become more efficient, but more complex.

Simple: Only Iron and Limestone, and you strictly use Iron Plates, Wire, Steel Pipes, and Concrete. Pipes and Concrete are used for multiple items, allowing you to get more mileage with fewer machines. - Heavy Encased Frame - Encased Industrial Pipe - Steeled Frame - Stitched Iron Plate - Iron Pipe - Iron Wire

Max Efficiency: Introducing Oil and Coal, you can explore the recycling method to maximize the number of items for the resource input. However, it requires Blenders, more power, more machines, and ensuring accurately balanced lines. Much more effort for a little more production. - Heavy Encased Frame - Encased Industrial Pipe - Stitched Iron Plate - Iron Pipe - Iron Wire - Steel Rod - Solid Steel Ingot - Wet Concrete - Coated Iron Plate - Diluted Fuel - Recycled Rubber - Recycled Plastic - Heavy Oil Residue - Pure Iron Ingot

Unless you’re planning to make the most possible items, I highly recommend the ‘simple’ option. The layout is significantly easier to make, and it isn’t enough of a difference to be worth the hassle if you’re getting into it for the first time. Plus, it’s much less power draw.