Question: I will be playing my first 5e session here soon. I got to skim the basic rules PDF, so I know that it plays a bit like 3.5 with some modernization. (*Please don't stone me if I'm oversimplifying that*.) I'd like to know what I should bring in my dicebag.

*I know that it's usually best to have one of each dice in D&D, regardless.*

That's not the point. The point is that I'd like to know if gameplay can be improved/hastened by having multiples of any of the dice.

For example, casting *fireball* in 3.5e without a big stack of d6's was a *very slow task*.

Likewise, there were many, many instances in 4e where multiple dice of the same kind were rolled. Especially so for damage rolls on Encounter/Daily powers: [2w], [3w], etc.

**Would be wise to bring extra dice of certain types?** I'm open for **theory** based on your understanding of the rules and what **may** come up as much as I'm interested in **personal experience**.

Answer: 
The dice I always seem to be short on are d4s. For healing potions and magic missiles, mostly.

Two d20s is essential, for rolling with advantage.

But seriously folks, there's no such thing as "too many dice" :-)
In my experience (I have a 5th level Ranger/Rogue in my current group), and if getting more dice isn't a hassle, I would for sure bring **2 D20(for when you need advantage or disadvantage), 1D12, 1D10, 1D8, 1D6, 1D4** for each player. 

*Additionally* I would look at each player to see what their most common attack is. For my ranger I use a short bow, with Hunter's mark, and Colossus damage often. (2D6 and 1D8) So as far as additional dice it all depends on what characters and their attack rolls they use the most. From the sessions we have played together we have 10D6 for a fireball and then borrow others dice when we score a critical and roll double or just roll it twice. 

In conclusion if I was a new GM I would again bring **2 D20,1D12,1D8,1D6,1D4, per player and have 1D12, 1D10, 2d8, 10D6, 2D4** on the side so they are quick to grab and use for when players score critical hits or when their attacks involve multiple dice. These are the dice I have used most often in my games. You could always have even more dice on the side if you are worried but that is where I would start.