Forest caves are the easiest cave to navigate. Spawning in Jungle and Forest biomes, they have a lot of grass and soil, and can help you get some resources. The Earth Crystals on the ceiling, which you can throw once collected, can help you fertilize nearby blocks, making it easy to create farms.
Ice caves, found in snowy biomes, are easier to navigate than forest caves, but a lot of Ancient Ice found on the floor makes it harder to maneuver. The low temperatures of the caves render your movement far slower than normal. Collect Blue Ice Crystals; they can help you freeze blocks when thrown, a feature especially useful in hot environments.
Find a hot biome like a desert or savanna? Chances are, you’ll find a lava-filled Fire Cave there. They are very hard to travel through without proper gear, but risking the journey is worth it: diamond ore found in these caves ALWAYS gives you twice the diamond when mined. Fire Crystals found in this cave can burn nearly anything when thrown!