Poison Resist Pots, keep a batch on you and a few at your respawn spot (I also keep extra food in case I need to do a corpse run).
Use fire arrows to burn spawners (Burial Pits and Pile of Bones).
Pull mobs back, dont rush forward until you are comfortable in the Swamps.
There is a mob that is like a troll but more fun, it hits like a truck but can be easily dealt with when you learn to parry it... just be careful as it repositions a lot which can mess up the parry timing.
Good items to prioritise are chains, you only need 10 Withered Bones to spawn the boss but you get loads of them, you really want a lot of chains and they can be scarce.
Kill leeches for bloodbags as they are used in a few good crafts, and entrails off Draugr for a good food item.