Tiktok ads: Does the engagement rate determine the ad spend?

I have been looking to expand my business from my small target niche to a broader audience, and I have observed that I need to increase my ad reach online. Therefore, I want to create an engaging ad for my Shopify store to run on Tik Tok. I have envisioned that creating more engagement will get my store more visitors and create a viral growth loop for me. However, I am not sure if creating an advert with high engagement levels will increase the amount I have to spend on my ad campaign and whether that will break even.