If you have FEZ then use it, but it's not mandatory to have it.
Because later monsters in the dungeon are quite evasive, Ancient Crossbow boosts the clear time by a significant amount because it lowers the enemy's evasion until the end of the fight.
Scaled Shield is important because the poison damages in percentage, meaning that Glacia will suffer. A lot.
With Scaled Shield, you will clear the dungeon at least 10% faster when compared to its unupgraded version, (U) Ancient D-hide Shield.
You'd want to get prayer points, ideally by Blessed Offering, and use the top two prayers for accuracy or max hit, depending on your situation. Check with Combat Simulator to see which is better for your clear time.
Maximized Farming
The rest of this guide is NOT for your first clear, your average clear, or even your first 100 clears. This is purely to maximize scrolls for any missing items. This will assume 99 in all skills, access to nearly all weapons and items in the game, and access to all DR and HP pets. This assumes you are (unless otherwise noted) using an optimal Agility setup, are using your best dps prayers, your best summoning synergy, and are using Diamond Luck Potions
Ranged
Cape of Prat is marginally faster than Maximum Skillcape, but as it more than doubles your ammo expenditure, it is not recommended.
This clocks in around 19 to 21 scrolls per hour, depending slightly on your Astrology bonuses
To use this method, you need to have 1090 HP and 57 DR. This is achieved by using Rocky Waters instead of Lake Swim. Any other method to get you to survive Glacia's damage is usable, but going to cost you more than 3% damage.
This clocks in around 19 to 21 scrolls per hour, depending on your access to Shield of Magic Power, and depending slightly on your Astrology bonuses. Worth noting that it will take longer overall to run this build, as the time to create all of the necessary runes will likely take longer than the time to collect the bolts. This build also requires the Power Shield to be able to survive and keep up in dps. Therefore, it is a fair bit less effective overall than the ranged counterpart.