Unless you're a 'solopreneur' running your own PPC consultancy, we strongly advise having at least 2 or 3 people involved in the trial.
Next to the account owner, it's very useful to have one or more other colleagues involved so you can have internal discussions about your trial experience and make a joint decision at the end of the trial.
If your PPC team consists of less than 4 people, we'd suggest involving everyone.
If you have 4 or more people in your PPC team, you could still involve everyone, but it would be wise to assign 3 'core users', preferably each representing different seniority levels. For example:
The team manager, which would usually also be the account owner.
One senior PPC specialist.
One junior PPC specialist.
What makes this core team different from other users, is that they are committed to spending enough time on a weekly basis to test TrueClicks during the trial period.
Ideally, these people like trying out new software and have some time available during each week of the trial.