Season Pass (15-25 dollars) Season Pass Bonus: Roy
DLC Pack 1: Returning Favorites (5-8 dollars)
Mewtwo (Free for owning both versions of the game)
Lucas
Wolf
3 Returning upgraded retro stages, Miiverse Stage (Free for owning both versions of the game), 4 new Mii Hats, 9 new Mii outfits (3 per class), Vs. Master Core Battle Mode, trophies surrounding star wolf team, Mother series, and some extra pokemon trophies
DLC Pack 2: Help our heroes! (5-8 Dollars)
Dixie Kong
Bandana Dee
Captain Toad
Daisy skin for Peach, Protoman skin for Mega Man with alternate final smash (flashes Roll, Auto, Tango, and Dr. Light instead of the Mega Men), James skin for Fox, New Mii Fighter class: Staff with 10 outfits to be unlocked, 8 new mii hats, 3 completely new stages. Ability to play non-omega mode with active stage hazards turned off.
DLC Pack 3: Returning Favorites II: Pokestyle (5-8 dollars)
Blastoise (Squirtle modified to be a solo character)
Venusaur (Ivysaur modified to be a solo character)
Ice Climbers (If they can figure out how to make them work on 3DS by this point, if not, Pichu)
3 Returning upgraded Retro Stages specifically including Saffron City and if Ice Climbers are able to be used also including Icicle Mountain, Raichu Skin for Pikachu, Igglybuff Skin for Jigglypuff, Charizard Y skin for Charizard with alternate mega form final smash, Extra Smash Run Maps based on Melee's Adventure Mode maps, Event Matches for the Wii U, Smash Brothers 64 demo for WII U, pokemon costume themed mii outfits and hats
DLC Pack 4: The New Challengers (5-10 dollars)
Isaac
Chorus Men
Dr. Luigi (Luigi/Dr. Mario Clone)
Flying Man
Inkling
Impa (In Zelda character tradition.... she is inexplicably a Greninja Clone)
Helmetless Samus Alt Costume, Donkey Kong with Boxing Gloves Alt Costume, An Alternate color for Bowser Jr's Skins, Dry Bowser Alt Skin, Ocarina of Time/Hyrule warriors costumes for Link, Zelda, Ganondorf, and Impa, Five New Stages (One is a Golden Sun stage, another a rhythm heaven stage, and another a Splatoon Stage), Alternate Game Mode: Powers Smash (You can play vs rounds with your Smash Run custom powers on as well as your custom movesets), New Custom Equipment, Extra Slots for Mii Fighters, And another new Mii Fighter Class. The best I can think of is Archer, but I'm not sold that's the best to go with.
I'd hand over my money in a second.