How many outlets can you have on a gfi breaker?

Depends on the breaker. If the load at the outlets is unknown then the standard rules of 80% apply.

You can only load a circuit 80% of it's maximum value. For instance, if you're connecting your GFCI outlets to a 15 amp breaker you can only have a maximum of 12 outlets.

If it's a 20 Amp breaker then you're allowed up to 16 outlets and so on.

In the US, you are limited to 13 receptacles on a 20 amp circuit and 10 receptacles on a 15 amp circuit in commercial or industrial installations. Any or all of these can be gfci-protected. You can install one gfci, the first one from the panel, and protect any or all the others from that one.