Skeletron:

• Shadow/Crimson armor is the better end, if you are a more experienced player, gold or sliver would work.
• Spiky balls, sticky grenades, or beenades are crucial in defeating skeletron, throw them at his head, and wait until he has low health, then take out a ranged weapon, musket or flail, and finish him off.
• ALWAYS bring at LEAST 5 healing potions, 10-15 is recomended