Sometimes you cannot simply gather items - you need a specific tool to do so.
Ore can be obtained with pickaxes.
Fish can be obtained with rods.
“The Old Pickaxe is the first pickaxe you can acquire. It is given to you when you meet the...Old Pickaxe
“The Forged Pickaxe is the last pickaxe you can acquire. It is able to mine Pyranium Ore, Glacite...Forged Pickaxe