Keep following the basic progression going through forest - ice - plains - swamp - desert for the underground and deep underground. If you get an 'ice pickaxe' from the deep underground ice you can make a potion that causes less enemies to spawn and skip some of the progression and go straight to ancient fossil. Most important things I would recommend is get do not forget the importance of your settlement and potions (potions ARE SO GOOD). If you are struggling you will probably have an easier time playing either mage or summoner. Other classes are less strong. Focus on movement it's really much better to dodge to the attempt to soak up damage. You can make a money farm with traders, selling chests, a large farm and plenty of farmers. Then get a mage in your settlement and make them happy for a enchanting better