Good evening Sarah and welcome back!
Thank you for reaching out to us.
I would love to help you with this topic.
Actually, you should be able to add additional fields on the tickets by using Event Tickets Plus.
In other words, if I understand what you want to achieve correctly, you do not need to purchase the Events Calendar Pro.
To achieve that, I would recommend reading the following: https://theeventscalendar.com/knowledgebase/collecting-attendee-information/
Let me know if that helps.
Have a great day!
Geoff B.