Brew up some poison resist potion and look for the nearest swamp. Be very, very careful because you are not fully ready to be here yet, but the next step is important. Sneaking in by land is an order of magnitude safer than landing by boat.

Look around in the swamp for a small plant with yellow flowers. It's very rare and difficult to find. If you are lucky you can skim the edges of a swamp, grab the seeds and go. Or if you are unlucky you will be carefully sneaking around, daytime only, looking for the dang thing and probably dying a few times while you're at it.

Then take your turnip seeds back to your base and get busy farming so you can move up to the next tier of cooking which will greatly help your HP and stamina.

As for the elder, you will want what it drops before you start mining iron from swamp crypts. The way I do it is a bit cheesy but it worked great when I was playing permadeath. Dig under the altar from 2-4 sides. You want a nice cave under there with several entrances. (It's even a mini-base because of the eternal fire on top.) Get a lot of fire and flint arrows and alternate them. (No point in using a fire arrow while it's still on fire.) Play reverse whack-a-mole. Ready your bow while you're still in the tunnel then fire off one or two arrows before ducking back inside. Make sure you have enough room in the outside ditch to get around the roots, but better if you go inside before those come up.