Many of the more interesting skill gems are only available after character level 19/24/31. Some even have to drop in game (not available as quest reward).
PoE has such a complex system of skills and support gems that you can make many skills do what you want. There are the "Faster Attack" and "Faster Projectiles" support gems, as well as several skills that can "fill the screen" as you put it - gems like "Fork" and "Chain" that can be applied to any projectile skill, or "Increased Area of Effect" for any AoE skill. Of course it takes some time to level your character and the respective skill/support gems to reach that level of destruction.