Wage your first war in the era of axes and chariots to eradicate a nearby rival and seize what will likely be a strong capital city. In this era, they should have only 2 or 3 cities, so the war will be short by default and net you land to grow and jump to a good lead. Avoid protective AI’s or AI’s with special bows.
Work toward the tech that lets you vassalize other Civ’s. While doing so, stick to limited-objective wars focused on defense or securing key resources, like if your land has no iron, but a nearby AI is sitting on a mine. Just grab what you need and no more as your economy grows.
Once you can vassalize enemies, you can start rolling to victory with a string of short wars. Capture just enough cities to make the AI capitulate, keep the best cities, gift back the rest, and you’ll begin to roll. You’ll soon hit a point where capturing 1 or 2 cities is enough to make an AI capitulate. Try to stick to one enemy at a time, as it’s harder or impossible to vassalize AI’s when you’re at war with too many of them. Wars become much shorter when you’re fighting to the point of AI capitulation instead of capturing every single city.