In order to make aerogel you need an aluminum oxide crystal and a gel sack. The wiki page says that gel sacks are best found in caves around the shallows and I find aluminum oxide crystals in the grand reef. Hope this helps out!
Fluffers there are light sticks you can use as torchest or plant on the ground if you need more light. If you built your base deep down these will help you out alot. If you want to save time and use commands to unlock them the item ID is ledlight.