Try to use up as little space of your city as possible, especially during Monkey v Monkey intensive play. If you need to prepare for an Impoppable tile or a powerful attack, you may find the need to place extra buildings, and in times of crisis, capturing enough land for the task in hand may be hard.
Try to save up Bloonstones. You never know when you may need them.
Try to reach Level 18 as quickly as possible. When you reach said Level, you'll be able to get Level 2 Banana Farms, allowing for a huge cash boost.
Always be prepared for early Lead Bloons, even on Round 1. For example, start with a 2/3 Boomerang Thrower, a 1/2 Dartling Gunner or a Bomb Tower/Mortar, or keep Pineapples ready in case they do show up.
Visit your city as often as possible, to gain the extra City Cash.
Remember to build as many Bloontonium Storage Tanks as possible and fill them up completely before attacking a MOAB Graveyard. Especially for players in Pacifist mode, it is possible to gain 5000 more than the storage capacity (10000 or even 15000 if two or all three tiles are nearby or if they are patient enough), allowing for an extremely powerful attack.
Before attempting to defend a hard attack, it may be a good idea to leave all money in your Banana Farms. They can provide an efficient disaster relief if you fail and have lots of money pillaged.
If this proves impossible, at least spend as much of your money as possible. This will decrease the profit made by others attacking you.
In some situations, it's more valuable to have none of your towers damaged than keep the money. If this occurs, try to have your bank at least 30% full.
In some situations, a decent computer is recommended, especially when micromanaging. However, sometimes, overly fast gameplay can make the same tactic difficult. A decent external mouse is also recommended.