Buy RS3 Spider silk
Spider silk is a hide dropped by certain spiders in RuneScape 3. Unlike other hides, it does not need to be tanned. You can use it right away with a needle and thread to craft spider silk gear.
Spider silk makes the fourth-best magic armour for free-to-play players, behind splitbark, batwing, and mystic. The robes need level 20 Defence to wear. The spider wand and spider orb need level 20 Magic.
With the right Crafting level, spider silk can be made into gloves, boots, a hood, a robe bottom, a robe top, a shield, a wand, and an orb. Level 27 Crafting lets you make the full set of robes, or level 24 if you skip the shield. Each piece of silk used gives 12.5 Crafting experience. It takes 15 spider silk to craft every item in the set.
Spider silk is also a component in crafting Masterwork blue cloth. It is tradeable and noteable, so it is easy to buy, sell, and store. This makes it a handy pick for training Crafting or gearing up a low-level mage.