You can preserve meat by making it into jerky. It takes 3 cooking, meat and salt. Swamps have salt water tiles, so it’s cheap.
Agriculture is good, but only if you intend to stay in one spot for long and have a way to preserve the results. Some plants never rot (cotton, wheat), some can be dried, others can’t be preserved (I think potatoes are like this).
Until you get agriculture up, harvest oaks for acorns and cook those.