Turnip seeds + cauldron upgrade. WIld turnips are kinda rare but very important, in my games I make a point to find them before even starting crypts. Read up on how stagger works, not getting staggered is very important.

Banded shield to max so you can parry abominations

Iron armor is actually kinda crap. Root is way better - it doesn't slow you down nearly as much and it has pierce and poison resist on it. Pierce resistance makes it quite strong against draugr archers and the odd deathsquito which are the most threatening enemies in the swamp by a huge margin.