Era 1 Engines
Use the Swallow (fully upgraded) from era 1 until you can get Falcon.
Your income is very low in Era 1. The Raven is slow and x7 more expensive to repair. Between the Falcon and Swallow, the Rhino is a good alternative.
Get all the upgrades for the Falcon and stick with it until era 2. The Falcon the most profitable engine of its era.
The Swallow is the engine with which you'll start at Era 1. and is most suitable for short tracks It pulls two wagons, has a medium acceleration. You can use it best to transport wood, grain, coal and iron.
Swallow Upgrade: Large steam dome (+1 Tractive force), Inlet pipe (+2 Acceleration), Steam header (+10km/h Speed) and Safety valve (+20% Reliability).
The Falcon has a medium speed and high acceleration and can pull up to three wagons.
Falcon Upgrade: Flux compensator (+1 Tractive force), Heat controller (+3 Acceleration), Coupling wheel set (+20km/h Speed) and a Control system (+1 Acceleration).