If you are impatient and like to play with all shiny toys right away. Even to upgrade buildings instantly to lv6. Just buy gems. Many people do so.
Me personally, I avoided to even build Trade Office for like 1 month, so I could enjoy the slow and methodical pace of this game without marble and hwp donations from guildies. So, when I got to 20k gems it was because it was piling on me, as I wasn't buying much for gems but the extra +10 licenses I needed for my island. For sure I was buying the license free deeds for coins, where I could.
So there was a time at lv50, when there was no lv75 stuff, I was doing daily logins in this game only in order to get my 10 gem pit spinning gems out. The only sense for them then I saw into buying 3 endless copper mines... nothing else really. When last gem pit went into dust, I basically bought all extra content in gem shop, that could not be bought with mere coins. These days I even buy extra jollies with gems. Still have like 70k of them left. Could buy yearly premium time... but... I am level 60 now, I have the granite masons, and I don't feel like some particular urge in leveling up. Slowly I will get there, I think... if I live long enough lol and BB won't shut the server ofc.
Like someone wrote above here... Do plan for 10+ years. Not just next 10+ months. Else you will end disappointed. This is afk game after all. It is not meant to be played like fps or rts. You log in and send gens... then you log off. Then later same day you log in, do combat for 1h, finish adventure and log off again. Unless you running it as some background task, though it is a wee heavy on my cpu tbh.