That's a big question.
The key element of this regime is transparency in public affairs. It's not a regime of prohibition; it's a regime of transparency. Influence is a natural component of democratic life. What's problematic is when certain individuals conduct influence activities on behalf of foreign states and they fail to say that they are working for a foreign entity. It's to bring transparency to public affairs.
The key measure of success would be the capacity to highlight the transparency of these arrangements with foreign powers. Another key success would be that the public is really clear about what the obligations are to register and that there's minimal confusion around the regulatory obligations and the system is easy to use. Then, though I do not wish it, one measure of success would be the capacity of the regime to identify individuals who do not wish to be compliant and make sure that adequate measures are taken against these entities.