so, I am stepping little bit into uncharted territory, for myself. I like being able to help people learn the basics of magic, and part of that is deck building.
this deck is just an example of a tribal deck that needs some serious work to make it usable. the sideboard is the final product, as it were, for contrast. no it isn't a "good" deck, but it is supposed to illustrate the concept of a tribal deck in a simple fashion.)
the description is just tips and explanation on how to build a tribal deck, and a little bit about how to use MTGvault to build such a deck.
My advice for a new deck builder is to pick a strategy or common theme that all your cards follow, and build around that. stick to about 60 (but no less) cards, and keep your lands between 20-25 cards.
when you are first learning to build a deck, the simplest way to build a cohesive deck with a theme or strategy is to build a "tribal" deck using all or mostly all the same creature type because they can build on each other and buff each other. like... inspiring veteran buffs other knights or Venerable Knight which can only give a counter to another knight creature when it dies. and non creature spells that either only work with your creature type, or work better with your creature type, like Joust. makes a knight bigger for a turn, and can kill an opponent's creature.
in the case of this deck I would recommend cards like History of Benalia. it creates knights, and then pumps knights. or Tournament Grounds. it helps you have the colors of mana you need for your knight or equipment spells.
the ideal way to look for cards for a deck like this is searching for cards with the tribe (in this case "knight") in their text. this will find you cards that specifically work with knights. buffing them, giving them abilities, things like that. these will make your deck stronger than just putting in a bunch of creatures because they share a creature type.
In this deck I see several knights, several soldiers, and... a Zubera. while it can be said that diversifying your threats is good, if you are looking to build a tribal (in this case knights) deck, having too many non-knight creatures is a hindrance, even if they seem to be good or powerful creatures, they often don't work with the core of the deck. so cutting creatures that are NOT knights would make the deck more consistent. in addition, seeing which knight cards are actually good, and which ones are just ok, and bumping those good ones up to 4 copies if you can, will also help.
for examples of what other tribal decks look like:
my Druid deck:
https://www.mtgvault.com/kazzong/decks/druidic-fury/
my defender deck:
https://www.mtgvault.com/kazzong/decks/defender-deck/
(strictly speaking it is a "tribal" deck because all the creatures share an ability, rather than a creature type, but the idea is still very much the same)
though these may not be the best of decks, they can give you a better idea of how a tribal deck functions.
from there you can start to understand what makes a specific tribal deck good, what archetype it fits into, and why. and how to create decks of other archetypes, even if they are not tribal decks.
hopefully this helps, and welcome to the wonderful world of deck crafting. :)
idea for the deck (mainboard):
I like knights, and big creatures. putting them together seems like it would work well.
lots of big flashy looking creatures that look like they will do cool things.
the idea for the deck (sideboard) is very simple:
play knights.
pump your knights.
get rewarded for playing knights.
swing big with your knights.
beat face with big double striking knights.
win.