Depending on the items you'd like to forge through the Maker skill, most armours and some weapons require Magic Powders. Monster Crystals, on the other hand, are forged from 100 leftover items of a monster of a specified level (refer here for a complete list); for instance, to forge Basic Monster Crystal 1, you'd need to have 100 leftover items from the same Level 31-50 monster.
Optionally, you may also improve your equipments' stats by Strengthening gems and crystals via your Maker menu. Each time you Strengthen a gem or a crystal, this will cost you 110,000 mesos, and you may end up with either a Basic, Intermediate, or an Advanced Gem/Crystal.
Also, you may only create items that are for your own class only. (For example, a Warrior cannot forge equipments from the Magician class.)
Scroll for Cape for Cold Protection 10% - With the skill Maker Level 1 and 50,000 mesos, forge this item with 100 Jr. Yeti Skin and 10 The Book Ghost's Sheet of Paper.
Scroll for Spikes on Shoes 10% - With the skill Maker Level 1 and 50,000 mesos, forge this item with 50 Poison Poopa's Poisonous Spikes and 10 The Book Ghost's Sheet of Paper.