I'm F2P and has 20 mil in reserve before nearly blowing it all on mods and leveling last month. The key was to maintain and (slowly) upgrade one simple but yet powerful squad did not require much adding on to it.
Obviously, this tactic was to only utilize a single squad, so there are many faults that come to it when F2P players hit level 85, where they need more than a single squad, or when they need many squads in a short timeframe (haha December Assault Battles).
I guess accelerated characters could have their leveling costs slashed in half or by a quarter. This way, it's easier to upgrade older characters, while the newer and Journey Guide characters still maintain difficulty.
