Advise from the Smash God himself.

Learning Classic Mode

https://www.youtube.com/watch?v=gYX4wWkX_Fo

Unlock All Characters Route

First things first, how to get a new save file.
What I did and seems to be the most reliable thing to do is copy your current smash save file to a USB Port.
Once you have a smash file on both your system memory and USB you can delete the save data from your system memory. This will keep the save data on your USB but still give you a new game on system memory. 
Turn off your WiiU once you Copy, and than delete your save memory off your system memory and remove your USB Port after the WiiU is turned off
Start up the game and now you can start the run!
Timer starts when you hit any button at the selection screen

Falco - Clear Classic
Wario - Clear 100 Man Smash
Lucina - Clear Classic on 5.5 or higher
Dark Pit - Clear All Star Normal
Dr. Mario - Clear Master Orders Hard
R.O.B. - 	Clear Crazy Orders after 10 rounds and defeat Crazy Hand
Mr. Game & Watch - Clear Classic Mode on intensity 2.0 or higher with 5 characters
Duck Hunt - Earn 1 KO in Cruel Smash

Listed above are all the characters you have to unlock and how to do so
I will put my current route that I think is the fastest and will edit if need be.

Classic 2.0 Ganondorf
Unlock Falco
Clear Classic 5.5 Bowser
Unlock Lucina
Classic 2.0 Rosalina & Luma
Classic 2.0 Ness
Classic 2.0 Captain Falcon
Unlock Mr. Game & Watch
All Star Normal
Unlock Dark Pit
Clear 100 Man Smash
Unlock Wario
1 KO in Cruel Smash
Unlock Duck Hunt
Master Orders on Hard
Unlock Dr. Mario
Crazy Orders (10)
Unlock R.O.B.

InprisonedShadow

RubberDuckyAssassin

yesman419

Super Smash Bros. for Wii U

Wii U

crazytonedog

DiamondPro104

naut05

USA / NTSC

Mario

Luigi

Peach

Bowser

Yoshi

Rosalina & Luma

Bowser Jr.

Wario

Donkey Kong

Diddy Kong

Mr. Game & Watch

Little Mac

Link

Zelda

Sheik

Ganondorf

Toon Link

Samus

Zero Suit Samus

Palutena

Marth

Robin

Duck Hunt

Kirby

King Dedede

Meta Knight

Falco

Pikachu

Charizard

Lucario

Jigglypuff

Greninja

R.O.B.

Ness

Captain Falcon

Villager

Olimar

Wii Fit Trainer

Shulk

Dr.Mario

Dark Pit

Lucina

Pac-Man

Mega Man

Sonic

Mewtwo

Lucas

Corrin

Bayonetta

Cloud

Co-op

Solo

Mii Brawler

Mii Swordsman

Mii Gunner

Solo Customs

Co-op Customs

Characters

All Star, Hard Subcategories

Classic, 5.0 Subcategories

All Star, Normal Subcategories

All Events Subcategories

Multiman Smash (10) Subcategories

Multiman Smash (100) Subcategories

Classic, 0.0 Subcategories

Classic 9.0 Subcategories

All Star Easy Subcategories

2nd Player

Ironman Subcategories

Super Smash Bros.

Surprises…

where the hell are my runs

Smash ultimate

100-man Smash Rules

New Speedrun Idea

True All-Star Mode with DLC

TheTrooble

Tech

KCCKirby

Frosted48

kaialb

abuela

xwpw4y0l

underscore58

Имя	Автор
Advise from the Smash God himself.	InprisonedShadow 9 years ago
Learning Classic Mode	yesman419 5 years ago
Unlock All Characters Route	RubberDuckyAssassin 7 years ago