At A Glance
- Invest first in the units you use in nearly every battle.
- Keep castle defenses and resource production progressing alongside your team.
- Avoid spreading materials across characters and utilities you rarely use.
Knowing what to upgrade first is one of the most important parts of Castle Busters progression. Early upgrades are relatively easy to recover from, but later investments can consume significant amounts of currency and materials. If you spend randomly, your account can become filled with half-developed characters while your main team struggles to keep pace.
First Priority: Your Core Team
Your main lineup should receive most of your early resources. Build around a small group of units that cover the essential roles you need rather than trying to keep every character at the same level.
A sensible core normally includes a durable frontline option, your best reliable damage dealer, and at least one support or utility character. Once those pieces are strong, you can begin developing alternatives for specific matchups.
Upgrade Your Main Damage Dealer
Increasing dependable damage often gives you the fastest immediate improvement. Better damage can shorten battles, prevent enemies from recovering, and help you push through opponents who previously survived long enough to overwhelm your frontline.
Do not automatically choose the unit with the highest theoretical damage. Prioritise the attacker you can actually keep alive and upgrade consistently.
Keep Your Tank Competitive
Your frontline needs enough survivability to create space for everyone behind it. If your tank disappears at the start of every fight, upgrading additional damage may not solve the problem. A few defensive improvements can sometimes provide a bigger overall gain than another offensive upgrade.
Upgrade Frequently Used Support Units
Support and control characters are easy to undervalue because their contribution may not appear as a large damage number. However, healing, slowing, stunning, shielding, or buffing teammates can decide close battles. If a support unit appears in nearly every lineup you use, it deserves regular investment.
Improve Core Castle Defenses
Do not allow your castle to fall far behind your battle team. Upgrade the structures that protect the most important routes and targets. A strong offense can earn wins, but weak defenses can make it harder to maintain progress.
Prioritise Resource Production Where It Pays Off
Buildings or systems that improve your regular resource income can be excellent long-term investments. They may not produce an immediate combat boost, but more coins and materials make every future upgrade easier to afford.
Prioritise economy upgrades that have a clear, recurring payoff rather than spending simply because a resource building has an upgrade available.
Choose Only a Few Utilities
Utilities can be extremely powerful, but spreading materials across too many options creates the same problem as upgrading every unit. Pick the tools you use most frequently and strengthen those first.
When Should You Expand Your Castle?
Expansion is useful when it creates a genuine advantage, such as adding a valuable building slot or opening space you can immediately use. Avoid expanding just because the option is available if you cannot afford to develop the new area afterwards.
Common Upgrade Mistakes
The most damaging mistake is trying to upgrade everything evenly. Other problems include spending premium currency to skip short waits, heavily investing in a new character before testing it, and neglecting the parts of your account that generate resources.
Before every expensive upgrade, ask whether it improves your main team, fixes a repeated weakness, increases future income, or strengthens an important part of your castle. If it does none of those things, saving is usually better.
Final Thoughts
The best Castle Busters upgrade path is focused rather than broad. Strengthen your core team first, keep key defenses competitive, improve resource generation where it offers a strong return, and avoid investing heavily in units or utilities you rarely use. Reassess your priorities after major unlocks and balance changes so your resources continue going toward the parts of your account that provide the most value.