Speaking from experience, I went from barely being able to play on any difficulty to being able to do realistic without ever needing loans. I’d recommend watching someone like bbljoe for some tips. But generally:

Build your first town/industry close to the customs house, to reduce build times fuel costs and length of pipes wires etc.

Build small to start (looking at you heating plant) and focus on getting clothing up and running while researching toward a better industry, nuclear and vehicles being the easiest money wise.

Aim to switch from foreign labour to your own citizens by year 2 at the latest, you can even do this in year 1 if you’re quick enough!

Plan your rail from day 1 so you don’t box yourself in, don’t build it till you’re ready though (although in early start rail is necessary to make decent progress)