It's been a while since I visited the world of Dungeons and Dragons. Had a bit of a rough patch with it, but found a new group and the game has since become just as fun as it used to be.
Perhaps the most defining mechanic of Dungeons and Dragons, and many other tabletop Role-Playing games, is the use of polyhedral dice. Sure, the usual cubic six-siders are in this world of castles and elves as well, but many of the dice we use to roll for Strength, Wisdom, Perception, and what have you, are these uniquely shaped ones that have more than six sides.
But there's a lot that can go into the arrangement and collection of game dice. You'd be hard-pressed to find a player with only one set -- many of us have dozens, if not hundreds of these little guys laying around, and an almost equal amount of players have fancy little bags to put them in.
Some players like to use specific combinations of dice to roll for specific things. For example, the Dungeon Master may call for a roll with advantage (roll two d20's and take the highest number) on your Dexterity check for, let's say, checking to see if a rickety bridge is safe to cross. The casual player may roll their d20 twice for this. However, another player may pass the dice they're to use around the table and have the other players give it a sort of good luck blessing, and then roll it. Others may pick a lucky die of a specific color for what they want to be the higher roll and another for the lower roll, and roll both at the same time. They could have a different die for each kind of check, one for combat rolls and one for interaction rolls, one for dealing with Goblins as opposed to Orcs, the list can go on and on. Many of the players I know even paint the 20 on their die green, and the 1 on it red for added simulation.
I personally like having dice that immerse myself a little bit more. I'm one who appreciates uniformity, and my characters usually wear very specific, linear color schemes. My Rogue, Narlan, wears all black with highlights of dark gray (as is normal for a character that's supposed to hide in shadows). My Fighter, Aladdar, wears shawls of gold and white, with ornaments of pearly yellow, gems of topaz, and other bright hues to show off his Pirate royalty. My Sorcerer/Warlock hybrid, Gideon (who also happens to be a character in my various writings), wears draping coats of blue with boots and gloves of navy. In these situations, I like having dice that represent the look of the characters, so I have a distinctly colored set for each of them that fit their outfits. For example if I'm playing a Druid in green (as seen below);
Then I would like to have a set of dice that represent the kind of stuff he would wear, or equipment he would carry.
It can swing a number of other ways as well. Maybe someone would have the mini pictured above and the same set of dice, but with a brown d6 to represent the wooden staff, or a blue d20 to represent his magic powers. Or the other way around, if they prefer. Or any other way, really. Dungeons and Dragons is a game about loose guidelines and adventure, so it can be basically whatever you want it to be, and hopefully behavior of such is encouraged.
I recommend the game to basically everyone. RPG groups are normally held at your LGS (Local Game Store) and I can't stress enough how important it is to support these places if they provide you with a comfortable place to play and amazing customer service.
