Having a variety of dice is great for a wide range of games and for quickly generating numbers and calculations. See below for some ideas for quick no preparation dice games for 2 or more players. Note: d10 refers to a dice with 10 sides, d20 has 20 sides etc
Sets of polyhedral dice are easily obtained online or from games stores such as Geek Retreat.
DiceShop has an amazing selection of all sorts of dice.
Polyhedral dice can also be found online.
If you don't have polyhedral dice they can be easily replicated: