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: 
Yes
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You should bring extra dice to *any* roleplaying event. In large numbers.

There are many situations where you need more dice and they are for the most part independent of the actual system you are playing:

* Maybe 5 enemies attack. All with the same stats. Roll 5 dice.
* Maybe all 5 hit and the character needs to dodge 5 times. Roll 5 dice.
* Maybe someone forgot their dice. Just give them half of yours.
* Maybe you got a bonus and your grenade or fireball does double damage. Roll all the dice together.

And finally, if the enemy evil boss monster has just one life left, the barbarian is taking a swing with it's double-bladed laser axe of instant doom aaaand... *you roll your single die a bit too enthusiastically... off the table, over the floor and under the cupboard*. That's it. The die is gone. End of epic scene. **Or** you just ignore that one die, take the next and kill the big bad evil guy.

Dice are dirt cheap. You need to make sure you buy *dice* and not *brand names*. If you do, a hundred will cost you less than a meal at your favorite burger place.

Bringing only a set amount of dice because "I don't need more" is like bringing a set amount of candy because "I will not want more". Yeah. Like that ever worked :)
This really depends on the level of the characters, if starting with level 1's then the basic 7 dice set, or pair of each is more than enough to cover you for a while. 

At level 5 you get access to extra attacks and to level 3 spells. There might be a need to add additional dice, lightning bolt/fireball damage starts off at 8d6. 

Having multiple dice is always useful for speeding up game play, but you're not throwing around massive damage spells or attacks every combat round, and with the mechanics of spell damage being based on the level slot you are not throwing around tons of dice for a level 1 magic missile. 

I play with my family and while still low level they each have their own base dice set and I have a few extras as the DM and it's been more than sufficient. A pair of each dice and a couple extra D6's will hold you over without slowing down game-play. 

I have not run any games above level 10, but a few extra dice D6 and D8 again and any dice related to your primary weapons would probably help speed things up a bit.