Excellent
This is the list of what I use.
Realm Works - Campaign management and rules management. This is what you read the story from. This is where you put the NPCs and the monsters.
Hero Lab - You have said you are playing D&D so I'll just assume it's 5e. You want to install the community pack (Check my signature). This is your combat manager and where you build the stats blocks for NPCs, PCs and Monsters. You store those stat blocks in RW though. My players all use Hero Lab to. Some of them use it digitally via laptop / ipad, the others just use printed sheets.
This is enough to play and gives you alot of power. I go a bit further though.
MapTool - This is the VTT I use. I play at the table using a Projector setup. This application is JUST to display maps on the tables. Technically, you could use this do also display tokens and handle any rolls. it's free btw which is why i use it versus something like Fantasy Grounds.
Syrinscape - I use this for music and sound effects. Technically this does not support playing over a network, but with some extra applications you could probably get this to work over a network.
Inspiration Pad Pro 3 - Check this out for a handy way to make random tables. It integrates quite well into Realm Works as shown
HERE.
Google Drive - This is where i store PDF's and anything else that doesn't really need to be in Realm Works.
DM Screen - I feel this is optional. I no longer use it but I have the laptop there which is kind of the same thing.
Hexographer - I think a map making program is a great addition. I don't use this one though. My personal recommendation is
Campaign Cartographer 3+. If you want to make maps then this software will let you build overland, dungeon, towns, cities, wilderness maps. You can also get an addon to create pictures of NPCs which is cool.
DriveThruRPG / DMsGuild.com - These are great resources for getting PDFs.
Kickstarter - Also a great place to get PDFs although the wait is obviously longer. I also get ALOT of minis from KS.
On top of this, use any resources you like as a source of information that you put into HL and RW.