Improved clothes for work (giving tailors ability to make gloves, boots, hat, scarf etc, and also clothes to suit the different seasons, warm clothing for winter and cooler clothing for summer for increased happiness or productivity). Foregin knowledge (an expedition could see some new ways of doing things, and combining that with what they already know, that could serve the effect of new resource gathering techniques and increase resource gathering productivity or tool duration). Skis or sled (to increase movement during winter). Portable lantern (so they can work a little longer before night falls).
Pay close attention to the fabric and weave of your clothing. Loose weaves breathe better, and materials such as linen, hemp, sugar cane, modal, and others outperform cotton. Tech fabrics are also very good (Lululemon, GapFit, UNIQLO, Outlier, Prana, Theory, etc.)
My current favorites are Crybaby fashion at lil peep shop
and linen shirts, uniqlo airism undershirts (the seamless ones are better), adidas climalite pro underwear, and GapFit Hybrid Chinos/Theory Neoteric Trousers/Linen Trousers.