Charcoal, then Alcohol

If there is enough organic matter to live from, there should be enough organic matter to turn into some kind of bio-fuel. Skip parts based on available tools/materials.

Mine some ores with stone tools. Make copper/bronze ones using wood to melt those. Turn wood to charcoal for forging steel to work towards steam engines. At which point you can start machining better parts for better engines.

Once you have precise engines you don't go for other fossil fuels. Machine the parts to make a still, and make alcohols. They burn well, and engines run very smooth on it. It just isn't commercially viable, and about 1/3 less energy dense than the average fossil fuels but that doesn't matter when you only require enough to jump-start your tools-to-built-the-tools chain.

Once you get to the point where your tools you can build solar panels, batteries, and electric motors you only require fuels for plastics (if you decide to use them), which can be made from the things like maize or olives.

Bio-fuels quickly become a dead-end when you need multiple times the amount of land you would need to feed a group of people who could do more work. Once you get to solar, you could scale up or move towards fusion/fission energy sources. At which point you'll have enough power to serve until you reach your space-age tech.