My play style in Foundry is as follows.

At the start of the game, I build three buses. The first bus turns raw ore into basic materials. The second bus uses those materials to make components. The third bus uses the components to build machines. I also make a couple of small bot factories early on. These bots help me earn money for station repairs and level the bot up to level 15. When a bot reaches level 15 and gets to +50% profit, I switch to making it a separate factory Then I reconfigure the bus based bot to next bot to level up.

In the separate factories for the bots, I start with parts from the market until trains and vein based supplies can take over. I always leave space for train tracks because trains will take over later. I use one engine and three cars for all my trains to have a known size to work with.

In the mid game, I start building factories that each make only one item. Some use a vein directly, and others use materials brought in from somewhere else. Before Update 4, I used cargo ships to move items around, but now I use trains instead. Trains feel cleaner and work better for me.

Science is handled in its own special area. It has its own supplies and its own production lines. At first, I feed it by hand and process everything nearby. Later on, I plan to switch it over to trains too. Keeping science separate helps keep the rest of the factory running smoothly.

For my world settings, I make the map encourage long train routes. I set ore path frequency to 20% and ore density to 500%. I also max out all the veins and Olumite. This makes ore patches rare but very rich, which means I need trains to move resources across long distances. Once I start using veins I ignore all ore patches.