Late to this, but the dollar amount matters less than people think. What we see on client accounts is that Google's trust checks hang on a few events, not on total spend:
- the first threshold charge going through cleanly. A declined first charge hurts more than a week of low spend helps;
- advertiser verification done with data that matches the payments profile (same legal name and country);
- no links to previously suspended accounts through payment methods, domains, or the same users and devices.
So $20-50/day on a compliant offer for a week or two is fine as a warm-up, but if the account gets linked to old suspensions, it doesn't matter whether you spent $200 or $2,000.
For restricted niches specifically: a lot of them are restricted, not banned. Gambling, some financial products, online pharmacy and similar need certification per country. Once that's in place you can run them openly, and that holds up far longer than warming an account and switching the landing page later, which is exactly what circumventing systems bans are built to catch.
That's most of our work at PPC Rebels: getting verification and certification sorted on agency accounts before anything goes live.