KISS.
Keep it simple, stupid.

At the beginning the project is nothing but an idea. If you get it off the ground, that's already a huge success. Rich features and code quality should be the last of your worries in this case.

Throw out any secondary functionality out the window from day 0. Make it work, then add flowers and shit (note to self: need to make way for flowers and shit).

Nevertheless code quality is an important factor, if you can afford it. The top important things I outline in any new non-trivial project:
1. Spend 1-2 days bootstrapping it for best fit to the task, and well designed security, mocking, testing and extensibility.
2. Choose a stack that you'll most likely find good cheap devs for, in that region where you'll look in, but also a stack that will allow you to spend most of your time writing software rather than learning to code in it.
3. Talk to peers. Listen when they tell that your idea is stupid. Listen to why it's stupid, re-assess, because it most probably is stupid in this case.
4. Give yourself a good pep talk every morning, convincing you that the choices you've made starting this project are the right ones and that they'll bring you to success. Because if you started such a project already, the most efficient way to kill it is to doubt your core decisions.

Once it's working badly and with a ton of bugs, you've already succeeded in actually making it work, and then you can tackle the bugs and improvements.

Some dev is going to hate you for creating something horrific, but that horrific thing will work, and it's what will give another developer a maintenance job. Which is FAR, far more than most would get by focusing on quality and features from day 0.

Most painful code error you've made?

More than I probably care to count.

One in particular where I was asked to integrate our code and converted the wrong value..ex

The correct code was supposed to be ...

var serviceBusMessage = new Message() {ID = dto.InvoiceId ...}

but I wrote ..

var serviceBusMessage = new Message() {ID = dto.OrderId ...}

At the time of the message bus event, the dto.OrderId is zero (it's set after a successful credit card transaction in another process)

Because of a 'true up' job that occurs at EOD, the issue went unnoticed for weeks. One day the credit card system went down and thousands of invoices needed to be re-processed, but seemed to be 'stuck', and 'John' was tasked to investigate, found the issue, and traced back to the code changes.

John: "There is a bug in the event bus, looks like you used the wrong key and all the keys are zero."
Me: "Oh crap, I made that change weeks ago. No one noticed?"
John: "Nah, its not a big deal. The true-up job cleans up anything we missed and in the rare event the credit card system goes down, like now. No worries, I can fix the data and the code."
<about an hour later I'm called into a meeting>
Mgr1: "We're following up on the credit card outage earlier. You made the code changes that prevented the cards from reprocessing?"
Me: "Yes, it was my screw up."
Mgr1: "Why wasn't there a code review? It should have caught this mistake."
Mgr2: "All code that is deployed is reviewed. 'Tom' performed the review."
Mgr1: "Tom, why didn't you catch that mistake."
Tom: "I don't know, that code is over 5 years old written by someone else. I assumed it was correct."
Mgr1: "Aren't there unit tests? Integration tests?"
Tom: "Oh yea, and passed them all. In the scenario, the original developers probably never thought the wrong ID would be passed."
Mgr1: "What are you going to do so this never happens again?"
Tom: "Its an easy addition to the tests. Should only take 5 minutes."
Mgr1: "No, what are *you* going to do so this never happens again?"
Me: "It was my mistake, I need to do a better job in paying attention. I knew what value was supposed to passed, but I screwed up."
Mgr2: "No harm no foul. We didn't lose any money and no customer was negativity affected. Credit card system may go down once, or twice a year? Nothing to lose sleep over. Thanks guys."

A week later Mgr1 fires Tom.

I feel/felt like a total d-bag.

Talking to 'John' later about it, turns out Tom's attention to detail and 'passion' was lacking in other areas. Understandable since he has 2 kids + one with special-needs, and in the middle of a divorce, taking most/all of his vacation+sick time (which 'Mgr1' dislikes people taking more than a few days off, that's another story) and 'Mgr1' didn't like Tom's lack of work ethic (felt he needed to leave his problems at home). The outage and the 'lack of due diligence' was the last straw.

So here's is the thing.
For some weird reason I decided to work at a VC funded startup. For 15k year,(I live in a really poor country).

So, let me describe the hell I'm in now, and if for some good grace you happen to be hiring, please consider saving me from the horror that's ahead.

Company got funded 5 months ago, main owners are, an economist and a civil engineer with no programming habilities whatsoever.

They took 1 month to assemble "a killer team", with no hiring expertise they handpicked a CTO that came in 1 month later and took a month of vacation in his first month of work.

He didn't do any specification of the system that needs to be built.

The 2 naive owners hired the rest of this "killer team".

The team is good, but have no appreciation of planning.

They've built and rebuilt the backend system twice, once in graphql and the second with plain http (is not real rest, just a http api), in front of, guess what a mongo database.

This mongo DB is not only one, but 7, because we have 7 microservices, and each has its own database.

After some time, they decided to fire their CTO, and hire one more programmer(that's me), because the CTO wasn't doing anything.

The app has 3 parts, the app per se, a business version, and a help desk, guess what the helpdesk just appeared last week on the radar.

Long story short, we have one month to deliver what couldn't be built in 5.

When I decided to work for these people, I did not imagine the kind of clusterfuck that I was getting into.

It took me 1 month to realize the whole situation, now, I really would like to see some help from the deities of any religion, not for the project, that project is doomed.

It's how I'll pay the bills after that clusterfuck collapses that worries me.

Now in the startup no one is talking about how stupid the whole situation is. Or how far back we are. And at this point there's very little that could be done about it, I have a feeling that it could still be accomplished, but it's fading day after day.

I will do my best to live the best of this experience, and do as the musicians in the Titanic and keep playing the music even after knowing the Titanic is sinking.

So today was my last day before heading off for an2 week holiday. Spent most of the day explaining to my team what needs to be done and how everything has been structured for the current project, but I get the feeling they don't understand any of it.

Pretty sure I'll be coming back to a clusterfuck.