The most important thing to know is that spoofing has never been safe. This is something that most of the experienced spoofers will tell you. Don't believe anyone that says or implies that it is or can be. Niantic 1st implemented a three strike system in May/June of 2018.

Niantic isn't obligated to issue all three strikes, as they can and have issued on rare occasions a permaban straight out. Some people thinks you will get the first two before the permaban is issued. If you receive strike one or two against an account, it's advised not to appeal it, as this can lead to actually having someone reviewing it and permanently terminating it.

This first strike or strike one is the first possible warning. If you receive this screen overlay, you won't see any spawns, unless you use an incense burner. You can use either the regular incense or the daily incense. You can do raids,and spin stops/gym disks. The friends list is closed until the ban is lifted. The first strike has also been called a shadow ban, this is from the early days of spoofing when basically you played in the shadows, and could only see common first stage Pokemon. The unevolved stages along with the uncommon and rare Pokemon didn't spawn. You may only get one chance at this before going to the second or third strike a.k.a. strike three. There has been many who've had several instances of strike one happening, it doesn't mean that you will be so lucky.

Strike two is a thirty day ban, that prevents logging into the game. During this time you are to be considering stopping/spoofing. The second strike has been known to drop without receiving the first strike or rw. This will result a blue screen up, and you won't be able to get past it, and into the account(s) that's received it until the approximately thirty days is up. This is supposedly your last chance to stop spoofing/cheating.

The one last is strike three that's the end for that account. This if you wish you can try appealing it, but understand that there's no guarantee it will be restored. Sometimes in the past Niantic has restored accounts. That though has been in the cases where they were catching those who played legit, and to many were caught.