Make torches from Lumps of Charcoal (burning wood in a furnace). You will need Coal for a lot of things later. Craft Super Glow Glass and cut it into slabs on a Circular Saw to get the most efficient light source.
The best fuel is Bottle Fuel that can be crafted in Biofuel Refinery from any 4 organic items (Sticks, Leaves).
Cheapest fertilizer is Mulch.
Super Glow Glass provides enough light for growing plants underground in adjacent tiles.
You can light cave surfaces from afar with Torch Arrows. But they don't always work.