Stick to the edges and scout out for Turnip seeds and kill drauger for sausage materials. Avoid diving in deep right away. Level up your food first. Typically I will do this before I even beat the Elder.

Scout around and look for the crypts and mark them on your map. Once you find a crypt or two scout out the nearest Black Forest location for a Copper node to mine and turn into a crafting facility. Not all swamps have crypts.

Collect guck form trees as you can, you don't need a ton of it but you will want it later.

Don't go in at night unless actually in a crypt.
Normally I will mine all night long and run it out to the local facility during the day. You can put a portal on top of the crypts to get back fast and repair quick at night. Stay rested, you can put a fire inside a crypt for comfort.