Cash cow (astronomically worse than voting/Gary unfortunately, pretty much not a viable way of getting cubits)
Or /prestige - Grind out the challenges, prestige and get cubits (requires VIP and the later prestiges requirements are so ridiculous it requires a ton of effort, so may or may not be viable depending on the time you can commit to it)
Other than that your only bet is buying em from the store for irl money or players.
Tldr; they made cubits way harder to obtain for f2p players since you've played.