How to Warm Up Google Ads Accounts?

I am new to making threshold accounts, but I've came in to some trouble with warming up the accounts. They all pretty much go in account review when I create my second campaign (first is the dummy one). I advertise Nutra products, so I don't know how long should I warm up the account for?

How do you create your first dummy campaign? I am stuck with this. I wish to warm up my accounts too but I do not know which type of campaign to use as a dummy one.