Mate, it's a nightmare!
If you don't abide by it and you get caught, no matter how small you are, there can be some pretty serious consequences.
What the EU should have done is said that AFTER 25 May 2018, all sites must comply and any new subscribers or account holders etc must see and actively agree and consent to their information being used. Current subscribers or account holders should have been left alone, but provided the same legal information with an option to update their preferences if so desired.
Alas, the ultimate wisdom from the EU will cause the likely decimation of so many business contact lists.