Starter Story · 2025-11-06

How I Built It: $400K/Month Mobile App

Julian Gargicevich, an Argentine developer in Australia, co-founded Gravl (originally Gains AI), an AI strength-training app, after a failing influencer-platform-turned-agency taught his team mobile UA. He rebuilt Fitbod's UX with a better workout engine in 2-3 months, launched with a Reddit 'how I built it' thread (300K impressions, a couple thousand users), then added subscriptions and paid ads. Spanish localization with sub-$50/day South America ads worked from the start. Now ~70K subscribers and $440K last month, with ~1/3 of revenue going to ad spend.

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8 tactics

Gravl · B2C · AI gym workout app

Post a 'how I built it' thread on Reddit with the technical details

300K impressions, a couple thousand users, and bug reports that proved demand

Posted a Reddit thread on how he built the app (then called Gains AI), sharing the technical specs. The audience was developers who like tech and may find the gym intimidating. The app was free at this point; the flood of bug reports and feature requests was the signal to add a subscription and start ads.

Workedpr-launchcommunity

Starter Story · 2025-11-06

Gravl · B2C · AI gym workout app

Copy a top app's design, but fix the part its users complain about

Founder says it gave the app its edge; no direct numbers

Dropped a me-too Hevy/Strong-style workout tracker that added no value. After a friend showed him Fitbod, he used it and researched it, finding its generated workouts weird and sometimes dangerous. Built 'Fitbod UI/UX with an actual proper workout engine' that accounts for equipment, weekly goal, gym frequency, consistency, gender, weight and age. MVP took 2-3 months.

Workedpositioning-nichefeature-development

Starter Story · 2025-11-06

Gravl · B2C · AI gym workout app

Start paid ads the day you add a subscription, once people want the app

First subscriber within 10 minutes; ads are the main channel at ~1/3 of revenue

Ran paid ads immediately after adding the subscription model, having first validated usage via the free Reddit launch. Spend is mostly Meta and TikTok, with a little Google and Apple Search Ads. Ad spend runs at about a third of revenue (excluding creative production). Advises validating that people will pay before spending on ads.

Workedpaid-socialapple-search-ads

Starter Story · 2025-11-06

Gravl · B2C · AI gym workout app

Translate the app to Spanish and run ads in South America for under $50 a day

Worked from the start and still does; US ads seen as too expensive

Both founders speak Spanish, so they translated the app into Spanish and ran ads in South America, spending less than $50/day, instead of starting in the expensive, competitive US market.

Workedlocalizationmarket-selection

Starter Story · 2025-11-06

Gravl · B2C · AI gym workout app

Pay creators ~$50 a video and copy what competitors run in Meta's ad library

Start small: pay creators as little as $50 per piece of content, use AI tools to generate videos and CapCut to edit your own. UGC is most of what works; AI video is cheap and easy to test. The hard part is volume, not making one ad. Use the public Meta Ad Library to see competitors' ads and where they put money, and copy what works.

Unknownugc-creatorspaid-social

Starter Story · 2025-11-06

Gravl · B2C · AI gym workout app

Ask detailed training questions up front, then show a 'building your plan' screen

Onboarding collects name, reason for using the app, experience level (advanced users get one-rep-max questions), goals, training frequency, split, excluded/focus muscles and gym equipment profile. AI is labelled throughout ('make sure that you are showing the users that this is an AI app, because that sells now'). A generating screen shows the custom workout being built, then a plan summary before the paywall.

Unknownonboarding

Starter Story · 2025-11-06

Gravl · B2C · AI gym workout app

Put a hard paywall right after onboarding, before people even sign in

Founder says 'a lot' pay before seeing the product; no rate given

Right after the plan summary, users hit a hard paywall before signing in for the first time; no free access to the product.

Workedpaywall

Starter Story · 2025-11-06

Gravl · B2C · AI gym workout app

Offer 24/7 in-app chat answered by a real person, not AI

Founder says they grew a lot with it and users value it; no numbers

In-app support chat available 24/7 with help articles and messaging; replies come from an actual person, not an AI.

Workedcustomer-supportretention

Starter Story · 2025-11-06

Numbers mentioned

Who	Metric	Value	Context	When
Gravl	revenue	USD 440K/month approximate	Last month's revenue ('over $440k')	1:11
Gravl	paying users	70K subscribers approximate		1:11
Gravl	revenue	USD 4M/year estimate	Host's extrapolation ('over $4 million a year')	6:51
Gravl	time to milestone	2–3 months estimate	Time to build the initial MVP	4:04
Gravl	views	300K impressionsper post approximate	Reddit launch thread impressions; 'a couple hundred likes within the first couple hours'	4:51
Gravl	users	first couple thousand users approximate	Users from the Reddit launch thread (free app at the time)	4:51
Gravl	time to milestone	10 minutes approximate	Time from activating the first ad to the first subscription	7:04
Gravl	ad spend	USD 50/day approximate	Upper bound: 'less than 50 bucks a day' on South America ads after Spanish localization	7:04
Gravl	share	33% estimate	Ad spend (Meta and TikTok, some Google and Apple Search Ads) as a share of revenue; excludes creative production	12:37
Gravl	team size	3 people		12:37
Gravl	team size	13–14 people approximate	Includes part-timers and contractors	12:37
Gravl	cost	USD 50K–80K/month estimate	Salaries (second-largest expense); period implied monthly	12:37
Gravl	share	15%	Apple's revenue cut	12:37
Gravl	share	1% approximate	'A 1% clip from revenue' (payee not stated)	12:37
Gravl	cost	USD 1,000/month approximate	MMP (mobile measurement partner) cost	12:37
Gravl	cost	USD 1,000/month approximate	Infrastructure: servers, AI bills and other tools	12:37
benchmarkMinimum cost of a piece of creator/UGC ad content	creator pay	USD 50per video approximate	'as low as 50 bucks for some piece of content'	7:53