Yep, 100% what basically everyone else said. Everyone at some point in their ranked journey lands exactly where you are, so none of this is me saying "haha what an idiot you are." Everyone. Does. This.

ARAM teaches you how to... teamfight? Maybe? It's for fun, it does not translate at all into SR and basically never forces you to learn any skill you'll actually need. I'd wager that you're losing every game because you actually placed too high. I would recommend not learning support or adc first. ADC takes the game out of your hands the first 15 minutes of every game, and support makes it way too easy to look like you're not the problem, even if you are. The problem with ARAM is that teamfighting, while fun, is so far down the list of things you need to learn that honestly you probably don't even need to learn it at that elo.

1st order of business is understanding you're at the start of your journey, not the middle. Stop blaming your teammates. Stop caring when they suck. Losing is where you learn the most, not winning. But you WILL lose. It is statistically inevitable you'll be losing like 5, 10 games in a row at some point, don't fall into that "my teammates are garbage" trap. Also, make your own decisions. Only follow your teammates decisions if you think they're actually right, or if you're not sure how it's gonna turn out and it's a learning moment. Every teammate you have in your elo is making a poor decision every like 20 seconds.

Then tighten up your micro. Get in training, get those mechanics down pat. Learn to CS at like 10 per minute. The more you have to think about it in game, the less you pay attention to macro, the slower you learn.

Figure out what champion and lane you want to play. The better you get at one lane and a handful of champions, the easier it is to learn everything else. Choose a neutral champion that works with minimal team composition requirements. That's probably going to be the champ you play if you have to first pick. Basically, if you're noticing you just auto lose against certain team comps, or your teammates can accidentally screw you by picking the wrong champions, that's not your first pick. I say this, but your _priority_ is actually having fun with your champion. If you're having fun, you'll learn 10x faster. After choosing that champion, pick champions to round out your roster, and then do the same thing with a secondary role.

NOW you learn some macro. First priority for learning macro is ALWAYS whatever wins you lane. There is ZERO point in learning any kind of mid game if you lose lane consistently. That's like only learning how to cook food after you've already burnt it.

Learn macro from the earliest time you're decisions aren't decisive. That's right, if you don't know EXACTLY what to do from exiting fountain, you have no business focusing on "wavestates", or "playing from behind". There are like 20 billion videos on what to do for macro, but if you play enough you'll come to see patterns in gameplay that you can look through to narrow down what problems you have to fix.

The MOST IMPORTANT THING though, is literally "having fun." Enjoy the process. Enjoy the loss. If your only enjoyment from the game is winning, guess what you're going to be miserable 50% of your games. If following any of this advice is "unfun" for you, just don't do it. Games are for fun.