You need to spend hive/sim tokens to buy assets/building to play the game = build your city.
Then you earning hive and sim tokens and it's up to you if you going to take your profits or build up your city and go higher in ranking for more rewards.
and it's trading game, so you can sell your assets anytime to other players, there will be also cards that you can only get by playing, and you could sell them or leave it for your city for better income. Some of them will be rare.
Do we need to worry about spending our tokens if we're not careful and can we make Hive tokens by unlocking achievements in game?
You need to spend hive/sim tokens to buy assets/building to play the game = build your city.
Then you earning hive and sim tokens and it's up to you if you going to take your profits or build up your city and go higher in ranking for more rewards.
https://dcity.io/info
https://hive.blog/dcity/@ironshield/introducing-dcity-io-a-fun-way-to-earn-sim-tokens-and-hive
and it's trading game, so you can sell your assets anytime to other players, there will be also cards that you can only get by playing, and you could sell them or leave it for your city for better income. Some of them will be rare.
Thanks for the clarification!