April 2017
I'm trying to get characters for my son's profile and outside of the gnome and snow globe challenge, I was wondering what the fastest way to obtain characters would be. Currently, I've been doing star challenges then going around the backyard and opening the 20k chests to buy the 75k packs. Is doing that and playing turf take over or another multiplayer game that gives you close to 20k tokens a match the way to go?
April 2017
Buying the Phenomenal Character Pack, which guarantees you a full character unlock every time, is definitely the fastest way to build your roster of the basic characters; just bear in mind that you won't get Legendary characters from that pack nor will you receive the specific characters released with the various DLC updates.
As for the fastest way to collect PvZ coins; I would suggest doing Garden and Graveyard Ops or if you're Multiplayer oriented go for Turf Takeover. Your total coin award from either is largely performance based, more so for Multiplayer, but on average you should be able to collect 20-30,000 PvZ coins from a really good full game of either.