Dungeons & Dragons Hardcover Rulebooks: Xanathar's Guide to Everything Expired

I started DMing about 6 months ago from a noobie perspective to DnD5e.
I agree with above comment. As silly as it does sound the DM guide is the least necessary.
I would start with the Starter Set which includes dice.
Then my purchase would look like this.
Battle Mat w 1"grid PLUS Clear Tablecloth && Wet Erase Markers.
Lay the clear table cloth over the battlemat and you never have to worry about ruining your mat.
Use Lego bricks or just marker to represent player position.
Finally I would start purchasing books in this order and NOT all at once.
1. Monster Manual
... Perhaps a few of the free 1shot adventures from DMGuild.com or spend a few bucks on a few. That gives you a feel for homebrew (when a user makes up their own story)
2. Players Handbook
3. Probably the upcoming book of times on inter planar travel.
4. Perhaps an adventure book like Tomb of Annihilation.
5. Finally you are ready to purchase the DM guide book.

Now here's why many of us feel the DM book is least necessary.
While it's true you need to know the core rules
- roll for initiative
- how spells and damage work as a whole
- how healing works
- how levels work
Those can be found in the Starter Set.
Dungeon Master Guide Manual is almost all about setting up your own campaigns

DnD 5e is ALL ABOUT making the game accessible.
It really is up to you the DM to decide what you will and not allow. If someone decides "every time I wake from a nap I'm allowed to fly for 5 minutes. You CAN allow this. Or you could say you can fly but only 30 seconds unless you have eaten a squirrel before your nap.
DnD is Soo much fun because its about weaving a story as a group.
Sure there are purists who will say the rules don't allow X but you as a DM can still role and roll whatever kind of world you want to create.

Ultimately the only thing you need to be a good DM us an imagination or the desire to increase your imagination.
Oh yeah and paper and pencils and one pair of dice.

The greatest challenge as a DM is shifting the story in response to player actions. You simply cannot be too rigid. You could spend a year crafting a campaign but if you don't allow the story the adapt it's dead on arrival.
Course you as a DM can force align your players and not allow certain actions which would destroy the story.

If you are a DM I would highly recommend the Player's Handbook, Monster Manual, and Dungeon Master's guide.

As counter-intuitive as it sounds, you could probably wing-it without the Dungeon Master's Guide, depending how creative you like to get. It contains a lot of valuable information about creating towns, adventures, enemies, items, and adventures and is filled with a lot of great ideas.

For example, D20SRD has a lot of information about navigating the environment (http://5e.d20srd.org/indexes/adventuring.htm) but the DMG has detailed information for how to deal with Extreme cold/heat, wind,rain, ice, altitude etc.

D20SRD has basic information about about vehicles (http://5e.d20srd.org/srd/timeAndMovement.htm) but the DMG will give you a suggested price if your players want to buy an airship (20,000gp!) as well as how fast it moves, how many people it takes to crew, and how much cargo it can hold.

Thankfully most all of the magic items from the DMG are listed in the SRD (http://5e.d20srd.org/indexes/magicItems.htm)

These are all things you can easily make up to fit your game, but it's nice to have guidelines.

Am I a dummy for just wanting to read this stuff but never play? Anybody remember the old Warcraft manuals? I loved that shit.