If you have customers and invoice them, or have suppliers and pay them then you are processing data and GDPR is relevant to your business.
There is an excellent resource for all small business owners. GDPR solicitor Suzanne Dibble has a Facebook group for small business onwers. She has a fab intro video into GDPR and a pack where you get all the legal items you need plus a check list. You do not need to purchase the pack to join the Facebook group. (But the pack is less than the cost of getting a new Privacy Policy for your website for example). There are over 30 free videos covering marketing, franchisors, therapists and more, and she answers questions. All the videos she has done can be watched, and they are categorised so you can choose the ones you think are relevant to you.
I would highly recommend Suzanne's 2 hour video on the basics before you do anything else. It has been invaluable to our small business, and from the comments I see in her Facebook group, she is helping thousands of very small businesses. jz993.isrefer.com/go/gdpr/CGo/
I hope it helps!
Caroline