Knowing what to spend Gems on is just as important as farming them. In Universal Tower Defense Z, Gems are the universal currency that drives every progression system — from summoning units to rerolling traits to expanding your team. Spending Gems on the wrong things slows your progression dramatically, while strategic spending accelerates it. This guide provides a clear spending priority system, cost-benefit analysis for every Gem use, and common mistakes that waste your hard-earned currency.
Gem Spending Priority Table
| Priority | Use | Gem Cost | Value Rating | When to Spend |
|---|---|---|---|---|
| 1 | Featured banner pity | 5000 | ★★★★★ | When S-tier unit is featured |
| 2 | Team slot expansion (5→6) | 500-1500 | ★★★★★ | As soon as affordable |
| 3 | Unit storage expansion | 200-500 each | ★★★★ | When storage is full |
| 4 | Trait Rerolls | 1 per token | ★★★ | After securing banner pity |
| 5 | Evolution materials | 1000-5000 | ★★ | Only when farming is slow |
| 6 | Cosmetics | Varies | ★ | Never — no gameplay value |
The hierarchy is clear: featured banner pity always comes first because a guaranteed S-tier unit provides the single largest power spike in the game. Everything else is secondary.
Featured Banner Pity — The #1 Priority
| Banner Type | Pity Pulls | Gem Cost | Guarantee | Value |
|---|---|---|---|---|
| Standard | 100 | 5000 | Legendary+ | ★★★ |
| Featured (S-tier) | 50-100 | 2500-5000 | Featured S/A-tier | ★★★★★ |
| Limited | 75 | 3750 | Limited unit | ★★★★ |
Why Featured Pity First
| Spending 5000 Gems On | Result | Long-term Value |
|---|---|---|
| Featured banner pity | Guaranteed S or A-tier unit | Unit provides permanent power |
| 100 random single summons | ~4% chance of Legendary per pull | Expected value: 0-1 Legendary |
| 100 Trait Rerolls | Small chance of Ruler (0.1%) | Expected value: likely no S-trait |
Featured pity provides a guaranteed high-value return. Random spending and other uses have much lower expected value per Gem. Always save for pity before spending Gems on anything else. See our summoning guide for detailed banner strategy.
Team Slot Expansion — The #2 Priority
| Upgrade | Gem Cost | Power Impact | When to Buy |
|---|---|---|---|
| 4→5 slots | 500 | +25% team power | Week 1 |
| 5→6 slots | 1500 | +20% team power | Month 1 |
| Extra preset | 1000 | Team flexibility | Month 2+ |
Expanding from 4 to 6 team slots provides a massive 45% increase in team power. The 5th slot lets you add a Support or Farm unit, and the 6th slot provides full team flexibility. This is the best value Gem purchase after featured pity because it immediately improves every game mode.
Trait Rerolls — When to Spend
Trait Rerolls cost 1 Gem per token (or are farmed for free from Challenges). Spending Gems on rerolls should only happen after you have secured your next featured banner pity:
| Reroll Spending | Gems | Expected Result | Better Alternative |
|---|---|---|---|
| 100 Rerolls (chasing Ruler) | 100 | ~10% chance of Ruler | Save 5000 for pity instead |
| 100 Rerolls (chasing Fortunate) | 100 | ~63% chance of Fortunate | Acceptable if you have pity saved |
| 500 Rerolls (chasing Sacred) | 500 | ~78% chance | Only with surplus Gems |
Never spend Gems on Trait Rerolls when you are saving for a featured banner. Free Trait Rerolls from Challenges, quests, and codes provide 5000+ per month — use those instead. See our trait reroll farming guide for free farming methods.
What NOT to Spend Gems On
| Avoid | Why | Better Use |
|---|---|---|
| Random single summons | 4% Legendary rate = poor value | Save for featured pity |
| Standard banner pulls | Lower rates than featured | Always use featured banner |
| Cosmetics | Zero gameplay impact | Any progression item |
| Skipping content | You miss Gem rewards from that content | Play the content instead |
| Speed-up items | Time saved < Gems spent | Farm actively instead |
The Random Summon Trap
| Strategy | 5000 Gems | Expected Result |
|---|---|---|
| Featured pity (100 pulls) | 1 guaranteed S/A-tier + 99 random | Best value |
| 100 random single (standard) | Expected ~4 Legendaries, 0 Mythics | 1/10th the value |
| 100 Trait Rerolls | ~10% chance of one Ruler trait | Poor odds |
Random single summons on standard banners are the biggest Gem trap in UTDZ. The 4% Legendary rate means you need 25 pulls on average for one Legendary — and there is no guarantee it is a unit you want. Featured pity eliminates this RNG.
Gem Budget by Account Stage
| Stage | Monthly Gems | Spending Plan |
|---|---|---|
| Beginner (0-2 weeks) | 5M+ | Expand team to 6 slots, then save for pity |
| Early mid (2-8 weeks) | 15M+ | 2-3 featured pities, expand storage |
| Late mid (2-4 months) | 25M+ | 4-5 featured pities, surplus on Rerolls |
| Endgame (4+ months) | 30M+ | Featured pities + targeted Reroll spending |
Beginners should spend Gems almost exclusively on team expansion and featured pity. Mid-game players can afford 2-3 pity pulls per month plus some Reroll spending. Endgame players have enough surplus to invest in trait optimization.
Gems per Hour — Detailed Efficiency Comparison
Every farming method in UTDZ has different efficiency, effort requirements, and accessibility. This detailed comparison helps you choose the best method for your situation:
| Method | Gems/Hour | Effort | Level Required | Team Required | Sustainability |
|---|---|---|---|---|---|
| Story Mode (speed run) | 300K-400K | Active | Any | AoE DPS team | Infinitely repeatable |
| Story Mode (first clear) | 200K-300K | Active | Any | Any team | One-time per chapter |
| Challenge Runs | 150K-200K | Active | Level 10+ | A-tier team | 3 per day |
| Raid Runs | 100K-150K | Active | Level 10+ | Co-op team | Limited by Raid tickets |
| Infinite AFK | 60K-100K | Passive | Level 5+ | AFK team | 24/7 sustainable |
| Daily Quests | 120K (15 min) | Active | Any | Any team | Daily reset |
| Weekly Quests | 100K (30 min) | Active | Any | Any team | Weekly reset |
| Codes | 210K+ (instant) | Instant | Any | None | Limited availability |
AFK Farming Detailed Setup
| Setup | Gems/Hour | Monthly Gems | Setup Cost | Notes |
|---|---|---|---|---|
| Basic AFK (1 DPS) | 60K | 4.3M (8hr/day) | Free | Minimum viable |
| + Farm (Fortunate) | 72K | 5.2M | 100 Rerolls | +20% income |
| + Support | 80K | 5.8M | Free | Buff increases clear speed |
| + 2nd Farm | 96K | 6.9M | 200 Rerolls | +40% income |
| Full optimized | 100K+ | 7.2M+ | Full investment | Maximum passive income |
Gem Spending Priority Guide
How you spend Gems is just as important as how you earn them. Here is the definitive spending priority:
| Priority | Spend On | Gem Cost | Expected Return | ROI Rating |
|---|---|---|---|---|
| 1 | Featured banner pity (S-tier) | 500-750/pull | Guaranteed S-tier unit | ★★★★★ |
| 2 | Evolution materials for S-tier | 100K-700K total | +200% base stats | ★★★★★ |
| 3 | Unit slot expansion | 500-1000/slot | More team flexibility | ★★★★ |
| 4 | Standard banner (A-tier) | 250/pull | A-tier units | ★★★ |
| 5 | Cosmetics | Varies | Visual only | ★ |
Gem Spending Mistakes to Avoid
| Mistake | What Players Do | Correct Approach | Gems Wasted |
|---|---|---|---|
| Random standard pulls | Pull standard banner hoping for S-tier | Save for featured banner pity | 100K+ Gems |
| Buying cosmetics early | Spend Gems on skins before building team | Only buy cosmetics after team is built | Variable |
| Skipping Farm investment | Not investing in Farm unit Fortunate | Fortunate Farm increases all future income | 3.8M+/month |
| Over-spending on Evolution | Evolving C-tier units | Only evolve S/A-tier units | 200K+ per wasted evolution |
| Ignoring code rewards | Not redeeming codes before spending | Always redeem free codes first | 210K+ Gems |
Weekly and Monthly Gem Income Calculator
| Source | Daily Income | Weekly Income | Monthly Income |
|---|---|---|---|
| Story Mode (1hr/day) | 300K | 2.1M | 9M |
| Daily Quests (15min) | 30K | 210K | 900K |
| Challenges (3/day) | 50K | 350K | 1.5M |
| AFK Infinite (8hr) | 80K | 560K | 2.4M |
| Codes (average) | ~7K | ~50K | 200K+ |
| Weekly Quests | — | 50K | 200K |
| Total | 467K | 3.32M | 14.2M+ |
With a Fortunate Farm unit, all of these figures increase by 20%, adding another 2.8M+ Gems per month. This demonstrates why the Fortunate trait is the single most impactful early-game investment.
Frequently Asked Questions
Should I save Gems or spend them immediately? Save for featured banner pity (5000 Gems). Do not spend Gems on anything else until you have pity saved. Once you have the guaranteed pull, you can consider other uses.
How many Gems should I keep in reserve? Always keep at least 5000 Gems in reserve for the next featured banner. Never drop below this threshold unless you are making the guaranteed pity pull.
Is it worth spending Gems on evolution materials? Generally no — evolution materials can be farmed from Raids and Story Mode. Spending 5000 Gems on materials provides less value than spending 5000 Gems on a featured pity pull that yields an S-tier unit.
What about spending Gems on Stat Rerolls for relics? Stat Rerolls are extremely limited in value compared to banner pulls. Only spend Gems on Stat Rerolls if you have surplus after all banner and expansion needs are met. See our relics guide for relic optimization strategies.