My new year resolution is to start to learn how to fight and i am starting even a bit before, my question is...

Regular sparring means its a place where they actually learn useful things compared to a mcdojo. They wouldn't let a brand new guy spar anyway nor do most places spar hard.

Boxing is the most straight forward, no bullshit option and will give you a guaranteed edge against a single opponent or at least a chance at defending yourself successfully against multiple attackers.
Muay Thai is great but good luck finding an actually legit place to train. It's also way riskier in regards to injuries and harder on the body specially since you're considering competing.
BJJ is GOAT if you're fighting against one person, good luck defending yourself from more than one while on the ground though.
Krav Maga is king of McDojos, but if by some miracle you find a legit gym with actual sparring instead of just CMA-like exhibitions, go for it, it's the ultimate jack of all trades in terms of self defense.
Universal MMA is mostly a meme and should be avoided unless you go train at some big shot's academy, like renowned UFC fighters and the like, otherwise stay away.

>McDojos
I don't get the hate for them, if the instructor is some guy who was known internationally and has some wins under his belt why would you care if its an "mcDojo" or not. The instructor is 99% of whats important when searching for a gym.

Kickboxing isn't too bad

Try BJJ with Muay Thai/ boxing. For a mix of ground and standup. Make sure you can get some sort of trial before you commit to it. Real schools want students who want to be there.

Semi-professional level fighter here in a few disciplines. As covered above, find an MMA gym that covers both striking (only would rec. boxing, Muay Thai, kickboxing) and grappling (BJJ, wrestling) as well as conditioning classes. Additionally, good gyms will have daily (light) tech-spar (with private time for pads with coach) as well as a weekly or bi-weekly full spar leading up to a fight. If there's no sparring whatsoever your form will go to shit in any real situation and you will act like it's your first day. You won't spar right off the bat, they will obviously lead you up to it and place you with similar size/experience opponents.

Go for boxing dude.. Most fight stay on the legs

Well put

Regular sparring dosen't mean that you always need to go 100% full contact kill mode, but you need to get used to the dynamics of fighting an opponent who is actively putting up a fight. A martial art that dosen't do any form of sparring is glorified dancing at best.

I took boxing, sparred 3-4 times a week, got concussed 3 times in 2 months, took 4 months to fully recover.

Be careful. Boxing is the most effective for the street alongside wrestling/judo, but sparring WILL give you brain damage, so do as much conditioning, pard abd drills as possible relative to the amount of sparring, especially heavy sparring in big gloves (which add to brain damage).

Pads and drills*

I've been boxing for a little less than a year at this point. What I did is went to the seediest ghetto place I could find in my city, I got a few weird looks because I'm the whitest dude that's ever been in there, but for the most part nobody was hostile. I'd say this has the lowest chance of running into the "you aren't good enough to spar, give it 3 more months" trap.

The more ghetto, the better the gym generally speaking.

Just avoid the reformed thugs and assholes that spar too hard and are there to hurt people.

OP, you need a sparring partner you can trust. The best sparring is just light technical sparring where you pull your punches and kicks.

If this is your first time doing a combat sport I would suggest starting with BJJ (and get a few wrestling basics). You can go all out without seriously hurting people and you don't get hit in the head, and it's perfect for 1v1 self defense scenarios. I always tell people that everyone has a puncher's chance but when you get someone on their back they are fucked. So your best choice that you'd probably stick with is BJJ because in you don't get hit in the head and in 6 months you will be able to handle anyone your size if you can take them down.

Depends on how much time you have.

If you have a lot of time on your hands, I. E. More than 3 times a week then do muay Thai.

Otherwise do boxing.

Boxing is simpler and focuses on getting good at a few moves. Muay Thai has more moves to learn so you need more time to get good.

Don't spar 100% and you'll avoid brain damage.

mcdojo-faq.tripod.com/
Read this. If its an internationally known guy that knows his shit and intended on teaching people properly instead of doing it purely for the money he wouldn´t let you avoid sparring.
An instructor that doesn´t do sparring is only good if he tells you that its merely fitness and not fighting, otherwise he is either incompetent or greedy.