[RPG] Will there be Dungeon Master Kit for 5e

You're new to RPGs and you're looking for the sign that says "New GM Orientation"… but there isn't one. Most of us learn by doing, or by playing with a more experienced GM. There isn't really any beginner's bible. We do have some already-answered questions around here that should give you some context for your experiments, though.

1. Consider if you actually want to GM right away or if you'd rather learn by playing in someone else's game. (Or if you're open to both.) That will affect how you approach the rest of the process.

2. Find a group. You need one of those either way. It can be online or in person, but it's easier to learn the craft of GMing in person, whether learning by doing or learning by playing in someone else's game. You might have to explain what roleplaying is if you're pitching it as a new activity to friends, so reading up on that might be good. There are some good examples of what roleplaying in D&D is like as well.

3. If you're GMing, figure out how to start the actual game. There are a few different ways you can start the game. Eventually you'll learn that how much and what you want to prepare before the first adventure is just a matter of your taste and GMing style, but until then you have to just get started and see how it goes.

This is just a very high-level overview of the process. Follow those links to the detailed sub-steps of each of those, with their own variety of decisions and possible different paths you can take.

From there it's all a matter of growing in skill and techniques through experience. GMing a game has a lot of bits and pieces to it – plot, developing situations, improvisation, acting, crunching math for NPC stats – and it can feel overwhelming. Greg Stolze has written a good walkthrough of the things that a GM does, putting them in context, giving advice, and presenting them in a not-overwhelming way and order, so that the bits all sort of fit together. It's called How to Run Roleplaying Games, and I highly recommend it. It's not the only way to understand GMing, but it's a good summary of the process of GMing in a mere 13 pages, and gives some things to try. It's worth a look.

The map/grid is optional item that the DM can use. It typically only used in combat situations, or in particular types of situations the DM deems that a map/grid is needed or could be of use. It allows for members of the party and in particular the DM to keep track of the creatures, and where they stand in respect to one another. As keeping things in your head can be a challenging task at times.

However in your example if a player wants to inspect horses, then you would just say they inspect it and have them roll an investigation check. No need to get tedious with movement. This allows for the game to be move forward and not get caught up in the numbers involved.