"You can start with $5/day" is technically true for Google and misleading for all three, because the platforms need a minimum volume of data before their algorithms work at all.
| Formal minimum | What it actually needs | Billing | |
|---|---|---|---|
| Google Ads | none ($5/day possible) | ~$50–100/day of spend to optimize | postpay, threshold billing |
| Meta Ads | no hard minimum | enough conversions to exit the "learning phase" | postpay, threshold billing |
| TikTok Ads | $50/day campaign, $20/day ad group | that minimum, plus a $50 first top-up | prepay — stops instantly at $0 |
TikTok is the strictest and the most cash-flow-unfriendly for a beginner: a hard $50/day campaign minimum, $20/day per ad group, and it's prepay in the US — your campaigns stop the moment your balance hits zero, no grace period, no credit. Its CPMs are low (around $3.50 globally vs Meta's ~$6.59), so the money goes far — but you have to front it.
Google and Meta both use postpay threshold billing — they extend you short-term credit and charge your card when you hit a spend threshold — which is gentler on cash flow. Google Search CPCs average around $2.69 in the US and are trending up; the practical floor to let Google's bidding learn is $50–100/day.
Meta has no hard minimum but the same underlying reality: the algorithm needs roughly 50 conversions per week per ad set to exit its learning phase, so a budget too small to generate that just never optimizes.
Realistic starting budgets: Google or Meta at $30–50/day for a few weeks to get past the learning phase; TikTok at its $50/day minimum, prepaid, and know it'll cut off hard if you don't top up. Below those numbers on any platform, you're paying to gather data that's too sparse to act on.