I mean, I'm having trouble deciding who I'll focus on, let alone devote most of my game-time to. Playing with friends I was able to play efficiently with all the characters in Brawl and most in Melee. So my question is whether or not you think you'll be able to get by online in Glory mode without spending all your time as one character.
Well, I can't speak for most of the community as a fact, but I would imagine that the majority of players have at least two characters, one that they "secondary" and one that they "main", with lots of "subs" for various situations.
A part of being a good Smash player is experience, and since each character plays differently and offers different levels of experience for the person playing them [such as differences in attack frames that teaches players how to time attacks better than if they stuck with the timing of just one character, etc etc etc], it's a good idea to have at least a few specific characters that you focus on perfecting.
But having one specific main player is always a good thing, because you can take all the accumulated knowledge and training you've done with other characters, the things that have improved your timing, reaction speeds, and knowledge of the characters themselves, how they operate and how to counter what they can do, and apply it as best you can to the character you are maining, so that you stand a better chance in competitive play against others.
Think of your characters as an army in Hyrule Warriors: Your subs are your standard soldiers, there for you to gain experience with.
Your secondary main is your general, a sort of second line of defense, one that you're pretty good with but not the greatest.
And your main, is your general, the toughest of your bunch, the one you've put through the most training and is obviously the most powerful opponent you can offer to your rivals.
No army is complete without a powerful and wise general.
So train an army, and get to smashing.^_-