The problem is of course that fighting tougher enemies with a low-level weapon not only requires you to repair it frequently, but it also takes a long time to defeat the enemy. But why fight with the lower level weapon? Simply pick your most powerful weapon, and quickly defeat the enemy. Now, before the slain enemy vanishes, switch to the weapon you want to upgrade. Since there is a small delay before the WHP for the defeated enemy is added, you can easily build up lesser weapons that aren't suited for the enemies you're fighting -- so that you can turn them into spheres and add their powers to your favorite weapon.

Dark Cloud Gem Attachments List
Looking for a quick and dirty listing of what the different gem attachments do for your weapons? Here it is:

• Amethyst: +10 Ice, +10 Dinosaurs, +10 Mages
• Aquamarine: +10 Ice, +10 Flyers, +10 Marine
• Diamond: +10 Metal, +5 to all other anti-enemy stats
• Emerald: +10 Magic, +10 Dinosaurs, +10 Plants
• Garnet: +5 Attack, +10 Fire, +10 Stone, +10 Flyers
• Opal: +10 Endurance, +10 Metal, +10 Mages
• Pearl: +10 Endurance, +10 Thunder, +10 Undead
• Peridot: +5 Attack, +10 Holy, +10 Plants, +10 Beasts
• Ruby: +10 Speed, +10 Fire, +10 Mimics
• Sapphire: +10 Magic, +10 Wind, +10 Flyers
• Topaz: +5 Attack, + 10 Undead, +10 Flyers
• Turquoise: +10 Ice, +10 Stone, +10 Mimics