I have some experience with gml and use Gamemaker studio 1.4 to code. I can't do pixel art and I have never published a game before.  I have made many simple games and never released them because of reasons. I'm 13 years old and I'm wondering if I should join. Should I?

Actually everything you've said is a reason why you should join.

Game Jams help developers get a project out the window, even if it's very limited and lacks polish. You might end up with something you build off from and make it a complete game. Plus, you get to say "I've been making games since I was 13 years old", something which others will find pretty impressive once opportunity arises.

If you're worried about your abilities, don't worry, this is just a start. No one's going to discredit you for trying.

I'm working on gms 1.4 and I can do pixel art and 2d art, I wouldn't might having a new person to game jam, I'm new to game jam.

Having been participated in several game jams (6+? I've lost count...) I would suggest joining a game jam if you want! It is a great opportunity to release a game you've made out in the world. My games gathered dust on my hard drive until I joined my first game jam!

Here is some advice I would give myself if I could go back that may help you:

• Keep your ideas for the game jam simple. Especially in 3 day jams, time is of the essence! Do not aim for a completed game, or even polished game, because frankly you will not have time (no one does).
• Plan ahead if that is your thing, or don't, but make sure to do whatever suits you best! Do what you know and is fun for you, not necessarily what you view as the most 'productive'. Many times I read people saying stuff like 'plan out your game ahead of time' and stuff, and while that works for some (and that's fine), it may not work for you. A three day jam is not the time to be trying different development styles! (Side note: I do not do any planning before a jam! Its strange, but its what works for me)
• Get sleep! Overworking yourself does not result in a good game! I would highly suggest NOT working all night to get extra features in your game, but rather getting enough sleep that you feel ready to work and have fun.
• Don't compare your games to others. Everyone who enters game jams have differing levels of experience. If you are happy with what you've made, then that is all that matters. Ratings/Comments/Downloads are nice, but having fun is the most important part. Remember, everyone starts from zero! No one got to where they are overnight! Even the most talented game developers started at the bottom, and had to make LOTS of games to get to where they are today.
• I cannot stress this enough, but keep your game idea(s) simple! Do not try to go into this planning to make a amazing entry. There simply is not enough time. Make a game that you find interesting, but is something you know you can (reasonably) achieve! Nothing is worse than having to quit because your idea was simply impossible given the time frame (trust me, I've had this issue a lot)
• Your (good, bad, or neutral) rating means nothing. Every jam I've been in has a rating system, and they all have their own flaws. Having lots of ratings does not necessarily mean your game is great, and having no ratings doesn't mean your game is terrible. It can be discouraging to get only a few ratings (or none), but just keep at it! Even when you get a lot of ratings, it doesn't mean anything! Ratings do not reflect the quality/fun/polish of your game! (BTW: I have nothing against having ratings in a jam! They just have some interesting flaws at times, and many people judge their game based on their rating, which can lead to disapointment if you get a bad ratings/few ratings)

I'm not sure how helpful the above advice is, but that is what I would tell myself if I could.

Game jams are fun and almost all of the jams I've been in have been friendly. I think this jam would be a great jam if your starting out!

The biggest thing is to have fun and not get discouraged!

I'd like to add to the list above:

• Get familiar with the basics before the jam.  You'll want to know how to move a guy on the screen, how to make a score, how to make a state machine.  Clearly you won't know how to do everything, but you should give yourself a toolkit of basic skills so you don't spend you're entire day making your player move correctly on the screen.  I really wanted dialog in my first game jam I participated in and I spent an entire day on learning how to do that.  This caused me not to finish :/
• META-STRATEGY: PRE-COOK OR BUY EASY MEALS AND SNACKS!!  Unless you've got a wife, girlfriend, boyfriend, or SO who is wiling to keep you fed during this ordeal, I highly recommend picking up some TV dinners, snacks, and drinks for the three days.  Nothing is worse than realizing your hungry and then spending the next 2 hours cooking because you're on an involved diet and you could have been making your game better.  Grab, reheat, go.

Thnx for the support! I've decided I'm going to join!

however, should I make/join a team or should I work by myself?

Do it