How to Build a Simple Mobile Game and Earn With AdMob

Every few months a new "I made $10K from a game I built in a weekend" video does the rounds, and every few months a wave of people burn a month on a game that earns $4 in its first year. Both things are true at once, and the difference usually isn't talent — it's whether you understood the mechanics of what you were building before you started.

I've built software for a living for years, and I finally sat down and shipped a mobile game the same way I'd ship any other product: pick the smallest possible version, wire up the monetization correctly from day one, and be honest with myself about what the numbers actually mean. This is the version of that process I wish someone had handed me before I opened an engine for the first time — what to build, how AdMob actually pays, and where people torch weeks of effort on the wrong details.

Pick the genre before you pick the engine

Most beginner guides start with "which engine should I use," but that's the second decision, not the first. The first decision is what kind of game you're building, because it determines whether ads even make sense.

Ad-supported mobile games work best when the core loop naturally creates breaks — a level ends, a run dies, a session pauses. That's why the genres that dominate the ad-monetized charts are the same handful every year:

• Endless runners (a death screen every 30–90 seconds is a built-in ad moment)
• Idle/incremental clickers (natural "watch an ad to double your offline earnings" hook)
• Simple puzzle or match-3 (a failed level is a clean interstitial slot)
• Reaction/timing games (short sessions, high replay count, frequent restarts)

If your idea is a slow-paced narrative adventure or a deep strategy game, ads will feel intrusive and your eCPMs will suffer because sessions are long and interruptions are rare. Pick a genre with a fast, repeatable loop for your first project — you can build something more ambitious once you understand the economics.

Choosing your engine: the honest comparison

For a first game, the engine matters less than people think, but here's how the major free options actually differ in 2026:

Godot is the best all-around pick if you're willing to write a little code. It's free, open source, has a tiny download, and its scripting language (GDScript) reads almost like Python. It's especially strong for 2D games, which is exactly the genre category above. This is what I'd point most developers toward, because it gives you real control without Unity's steeper learning curve.

GameMaker is the friendliest option specifically for 2D games — it combines drag-and-drop logic with its own scripting language (GML), so you can start visual and add code only when you need it.

Buildbox 4, GDevelop, and Construct 3 are genuinely no-code. If the idea of writing any script at all is a dealbreaker, these visual-logic tools will get a simple runner or clicker built without touching a text editor.

Unity remains the safest choice if you plan to scale past your first game — it has by far the largest tutorial library and the deepest mediation/ad-network ecosystem — but it's overkill for a first, tiny project and the learning curve will eat into the momentum you need to actually finish something.

My honest recommendation: if you can spare a weekend to learn basic GDScript, start with Godot. If you want zero code whatsoever, GDevelop or Buildbox will get a working ad-monetized prototype in front of players faster.

Build the smallest version that's actually fun

This is the step people blow the most time on. Scope your first game down to:

• One core mechanic
• One screen (plus a menu and a game-over screen)
• No multiplayer, no cloud save, no complex progression system

If you can't describe your game's core loop in one sentence, it's too big for a first project. "Tap to jump over obstacles, the game speeds up over time" is a complete game. Build that, make it feel good — tight controls matter more than content — and resist adding a second mechanic until the first one is genuinely fun to repeat fifty times in a row.

One mistake worth flagging explicitly: test on a real, low-end Android device before you submit anything. An emulator or a flagship test phone will lie to you about performance — frame drops, ad-load stutter, and layout issues around notches and gesture bars only show up reliably on the kind of mid-range hardware most of your actual players will own.

Setting up AdMob correctly

Once the game loop works, set up your AdMob account (it's free to create) and register your app inside the AdMob console to get an App ID — you'll need this in your game's code before you build any ad logic. Create separate ad units for each ad format you plan to use; don't reuse one ad unit ID across formats.

During development, use Google's official test ad unit IDs, not your real ones — serving real ads to yourself while testing can get your account flagged. Both major engines have mature plugins for this: Godot developers commonly use a third-party AdMob plugin (Poing Studios' is the most widely used) that wraps Google's official Mobile Ads SDK and also handles GDPR/UMP consent prompts for you, which you're legally required to show EU and UK users. Unity has Google's own first-party Mobile Ads SDK plugin, and as of 2026 you need version 4.2.0 or later if you want access to bidding-based mediation — more on why that matters below.

Which ad format goes where

This is the part that actually moves your revenue, and it's simpler than it looks:

Rewarded video is your highest-value format by a wide margin — in top-tier countries (US, UK, Canada, Australia) it typically runs $15–30 eCPM, versus a global blended average closer to $8–18. It's opt-in, so players choose to watch it, which is why it pays so much better than interruptive formats. Use it for things players actually want: an extra life, doubled coins, a revive after a death. Never force a rewarded ad — the whole point is that the player chooses to watch it.

Interstitial ads are full-screen and shown at natural breaks — after a level ends, on a game-over screen, between menu transitions. Tier-1 country eCPMs run roughly $5–8 (sometimes higher), with a global average closer to $2.50–5. Placement discipline matters here: fire one after every 2–3 game-overs, not every single one, or your retention will collapse before your ad revenue has a chance to compound.

Banner ads pay the least per impression but sit on screen persistently — a reasonable format to add once the core loop is solid, but not where your revenue will come from.

Once your basic setup is generating real numbers, mediation (layering multiple ad networks like AppLovin, IronSource, Meta Audience Network, or Vungle on top of AdMob) is the next lever — publishers who add mediation on top of a bare AdMob setup commonly see a 20–60% ARPDAU lift within a few months. It's not something to configure on day one, but it's worth knowing it exists so you don't leave money on the table once you have real traffic. One technical note if you're on Unity specifically: waterfall-style mediation for Unity Ads placements is being phased out (no new waterfall placements after January 31, 2026), so set up bidding-based mediation from the start rather than building on the older model.

Publishing: what it actually costs

Google Play charges a one-time $25 registration fee — no annual renewal, no per-app charges, ever. That's the entire cost of a Google developer account for life. Apple charges $99/year for the App Store if you want iOS too, which is worth knowing before you assume "free" covers both platforms — most solo developers launch Android-first for exactly this reason.

One 2026 change worth knowing before you publish: Google now requires personal developer accounts to run a closed test first — you need at least 12 testers using real Gmail accounts, and the app has to be actively used for 14 consecutive days before you can push it to a public release. Budget that two weeks into your launch timeline; it's not optional anymore.

The realistic earnings math

Here's where I want to be straight with you, because this is the part the "I made $10K" videos gloss over. A well-optimized game with 50,000 daily active users, running a healthy mix of rewarded and interstitial ads, can realistically generate $5,000–7,000 a month. That's a real, achievable number — for a game that has already found 50,000 daily players, which is the hard part.

Your first game almost certainly won't have 50,000 DAU. If you launch to a few hundred daily players — which is a genuinely good outcome for a first solo release — do the same math at that scale: a few hundred rewarded-ad views a day at $10–20 eCPM plus a similar volume of interstitials at $3–6 eCPM will land you somewhere in the range of tens of dollars a month, not thousands. AdMob pays out monthly, around the 21st, with a $100 minimum threshold — if you don't hit $100 in a given month, it rolls over to the next one.

That's not a reason not to build the game. It's a reason to think of your first release as a pipeline test, not a payday — you're proving you can build something, ship it, get real players, and read the resulting data. The ad integration is genuinely the easy 10% of this. Getting a few thousand people to actually play your game is the other 90%, and no amount of AdMob configuration will substitute for that.

Where to actually spend your effort

If I had to rank where a first-time mobile game developer should spend their limited hours, it's roughly: game feel and core loop first, a correct (not necessarily optimized) AdMob setup second, and marketing/distribution a close third that most tutorials skip entirely. Build something small enough to finish, get the monetization plumbing right the first time so you're not retrofitting consent flows and ad units later, and treat your first launch as the start of a feedback loop rather than the finish line.