Hi everyone,
I can see some good tips there! Well done guys.
I had the same issue with money at the beginning, and I noticed that you can handle it better by having a full control and awareness of your xp/level increase.
Increasing your level too quick will force you to spend more simoleons with road updates (really expensive), or other kind of new unlocks. The key is then to work on gaining money, by completing some epic projects to increase your population, without affecting your XPs, while making sure your population is fully happy. The increase of population through the epic buildings, and the construction of a few special buildings (that you can earn through the Season of the contest of mayor) will allow you to earn more taxe money from your citizen as well.
Thanks to this method, I don't really run out of simoleons.
Hope this can help too !!
EA_Michel