In terraria there are tons of armor choises and sets. they can go from very basic to hard to get, the easiest armor to get is wodden armor and one of the hardest it the beetel armor. Some armors give you a special effect when you equip a set of the samy type, like titanium gives a chance to take no damage every 10 seconds, or like the shadow armor will give you incresed movement and atack speed. Neocities.
the way you would gather materials for most armor sets it by finding metals down in the cave systems and chests, for example it might be hard to get iron thats close to the surface, but you will find much more deeper underground. many other metals man be found after defeating some bosses, the first boss you might come across is a giant eye, once you defeat the boss it will drop demonight or crimson ore, use these with a furnase to make the bars, same thing with all the other ores you will find on your adventures.
