Just bought Smash Ultimate and I've never played a Smash game before. There's so much to keep track of and I can barely keep up. I'm trying to get into the controls but there's items dropping everywhere, lots of effects in the background and some kind of tag characters that appear mid-fight. I'm honestly not sure what is happening and I often lose track of my own character because there's so much drama on screen.
How the hell do you learn this game in the best possible way? Should I turn every item drop off (if it's possible), stick to some less flashy/complex maps and then perhaps focus on simple character like Mario? I'm not even sure how to smash people off the map, or how to recover from a smash myself. Hell, I'm not even sure what an actual smash is.
You can turn items off in Smash mode, by going into the Advanced rulesets. I recommend you start playing on very plain stages such as Battlefield, against low level CPUs. There's no shame in doing that! You'll get better once you learn the ropes.
Those tag characters are Assist Trophies and Pokeballs - the former you can identify by it being those rainbow-coloured glass cylinders with the shape of a guy inside.
I do heavily recommend turning off items or, at the very least, going into training mode (it's in the Games & More section) and figuring out what each item does. Turning off items is better though cause then you can focus on learning the game.
Mario is a good choice to learn the game with, if you have unlocked Lucina, I would heavily recommend her over Mario because she's just about the most straight forward character there is, but also overall very good in teaching you the basics. Kirby also is a good choice for early learning because he has multiple jumps and a good recovery move.
As for what a smash is, I'll give you a rundown of what types of attacks there are.
Jab: Press the attack button while standing still.
Dash attack: Press the attack button while running.
Strong attack or Tilt: Press the attack button while tipping (!) the directional stick into one direction. There are 3 directions for the purpose of the moves - Side (colloquially referred to as Forward), Upward and Downward. These are a bit tricky to pull off, especially when you're new to the game, so I recommend you going into your controller options for your player tag, and putting the right stick (for Joycons, Classic and GameCube controllers), to "Attack". This allows you to do Tilts by just flicking the right stick, and you will never do Smash attacks.
Smash attack: Press the attack button while holding the stick into one direction. Again you have F Smash, U Smash and D Smash. Those are the ones you can charge.
Aerial attack: Press the attack button while in mid-air. Depending on which direction you press while in mid-air, you will be doing an aerial attack in that direction. Aside from F, U and DAirs, you also have an Neutral Aerial (no directional input) and, unlike the grounded moves, you have a Back Aerial as well that is different from the F Air.
There's also special moves (colloquially referred to as B moves, in reference to that being the default layout for specials on the GameCube controller), where you have a Neutral, a Side, an Up and a Down B. For most characters, the Up B is a recovery move that gives you some additional height on top of the jumps you can do.
And then there is grabs+throws, shield and dodging (directional dodging/rolls, spotdodge which is dodging without directional input, and airdodges, which can be done with or without directional input), but I wouldn't worry too much about those things when you're still trying to figure out how to do the absolute basics.
If you need help with anything, I'll gladly assist you. Feel free to ask!