Let's say, I'm a level 15 wizard. I cast demiplane, and put a clone in it. I die. Would I now be native to that demiplane?
Now I cast banishment, and enter my own demiplane 2000 Glyphs of Warding trigger, and after that I break concentration on banishment.

I return being buffed by every single buff in the game.

What have I read incorrectly?

The only thing that can be read as iffy is you being native to your demiplane. Otherwise, nothing really seems off here. Just remember each glyph costs 200 gold (unless you snag a bulk rate), so 2000 glyphs would be a whopping 400,000 gold; even a dragon has trouble fathoming that!

The wish (hope the link works) allows you to cast it for free. It's slow, but not that slow. The true polymorph might allow you to create kegs full of gold dust.

Assuming you only cast wish once a day (no boons), it would take just under 5 and a half years to get the glyphs. Plus, with that wish effect, there's a 1/3 chance you can never cast wish ever again. With true polymorph, your DM might but an end to your shenanigans, but you might have some fun!

EDIT: The effect doesn't have the 1/3 chance, sorry!

Actually it only incapacitates when the target is native to the current plane so it would work 

 Does this spell work against Nightwalkers? They're native to the Negative Plane, and the flavour text in MToF about bribing them with lives to return home makes no sense. Why would one agree to kill a few people and then return home when it would much rather stay and try to kill everyone? Besides, Nightwalkers have no language. Even casting tongues wouldn't allow you to communicate with them.

Great spell if you have two bags of holding

I've got an in person one-shot coming up soon, and it is made entirely of Feywild creatures in the Material Plane... Please tell me this spell doesn't send Banished creatures to a random space in it's native plane... I put a lot of effort into this, and might actually cry if my creatures get banished

The spell doesn’t say that they are transported to a random location, so you could say that they are banished to some sort of base or home on their native plane, opening up the possibility of their return to the material plane.

Yeah, well we started the one shot last week and now it'll be a two shot. We already started combat, but the Sorcerer hasn't thought to use banishment

I'm in a game and i was banished! how the heck do i get out of it. is it possible, or is my character screwed!? plz help. :(

Don't worry, if it's this spell and not one like Plane Shift, you will leave the banishing plane assuming you're native to the plane you are in.

It means if the creature you banish is from the same plane you cast the spell in, they get sent to a different plane for a short time before returning to the plane you banished them from.

So if the creature is from the mortal world then they usually* will reappear.

* Unless you're in Hell or something

Heya, genuinely concentration is broken if you are just incapacitated, it's listed as one of the things that causes you to lose concentration in the PHB, under spell durations: 

• Being incapacitated or killed. You lose concentration on a spell if you are incapacitated or if you die.

https://www.dndbeyond.com/sources/phb/spellcasting#Duration

I know it's odd, and I'd agree with you that being incapacitated doesn't mean you can't focus or think, unfortunately that's just the way its ruled o7

Imagine playing a character not from the material plane and this spell gets casted

If a teifling was born in the material plane would they be native to the nine hells or the material plane?

Here's where a lot of players get confused:

Banishment sends your target to a harmless demiplane and incapacitates them, if they are native to the plane you are on, for one minute. After one minute, or concentration is dropped, they return to the same spot.

If the target is not native to your current plane, Banishment sends them to their native plane and does NOT incapacitate them. They remain there until concentration is dropped. If you concentrate on the spell for the entire minute, the target does not come back, and remains on their native plane.

Quote from KaptainKittens >>

Unfortunately Banishment also incapacitates the target while they're banished, and being incapacitated causes you to instantly lose concentration ^^'

 If you are not native to that plane, it would send you home without incapacitating you

So can my wizard from the prime material plane, who is on the plane of fire, banish herself home again and maintain concentration for the one minute required to complete the spell?

Does she need to make a saving throw? 

Kind of strange the spell doesn't specifically include or exclude this behaviour as it must be the most commonly asked question for the spell...

"If the target is native to a different plane of existence than the one you're on, the target is banished with a faint popping noise, returning to its home plane. If the spell ends before 1 minute has passed, the target reappears in the space it left or in the nearest unoccupied space if that space is occupied. Otherwise, the target doesn't return."

Your wizard is on the plane of fire. Hes from the prime material. Yes he must save. If he fails he gets banished.

Willingly failing a saving throw is a house rule that the designers are okay with, but it is a house rule.

The answer to your questions are in the spell description, why would they need to add more text?