I may have a contrasting opinion here than most, but
This game is different to the other smashes.
There may be a few exceptions to the rule, but most characters in this game have similar option spreads and aren't technically intensive. Unique mechanics (usually in burst movement options like Pikachu's Up-B, Sheik's bouncing Fish, etc or SHULK) do take time a lot of effort to get used to for sure but are few and far between.
This game focuses on smarts and knowing what your own character and opponent's character can do. Playing everyone (or a lot of characters) seems to be the best means of improving in this game at this stage of the meta; ZeRo will attest to this. Learning the weaknesses and punishment windows of a character comes best from playing them yourself and that knowledge is easily applied throughout your character choices (due to similar option spreads).
This doesn't mean to say that who you use in tournament will be one of 50 characters, you should be confident in your pick and second guessing ever is detrimental. Towards the end of Brawl I would rarely if ever play my main (Marth) outside of tournament, but when it came down to it I wasn't bringing out my Falco (much), MK, ZSS, Fox, Dedede, TL, G&W, Sheik, Lucario ever, but to me it was more important to be comfortable with all the different options that existed in that game and apply them as necessary with my main (it's easy to be like "well my best move is fair, dancing blade, I don't ever need to shield, roll, spot dodge or whatever other options; because those unique options are better in those situations!" of course that isn't entirely true though).
However, I say this is effective for me and others because we already have a solid grasp on Smash and it's fundamentals that have ported over. We understand stage positioning, punishing, timing, patience and how various options work/how to use them, control and execution issues are usually minor. When new to the game/competitive scene, you're likely to find sticking to the single character and using them as a lens to view the game will be most comfortable for you, when asking for help a person may advise "do this instead in that situation" and while you may not question the implication of why that option was better than another, eventually the logic behind all these things come as straight forward (it's just about performance on the day of a tournament at that point).