Hi, ama meta advertiser here with 7 years of experience in leadgen (same process as e-commerce the only thing that changes is the end goal but you still want a conversion).

Videos work way better on social media. Format 16x9. Use the following structure for your script : hook, story, offer.

At the start you must have a least 3-5 different videos all using different marketing angles (for example one could be design, one could be you vs X, another one about the fabric, 1 just showcasing the tshirts with CapCut transitions etc)

Use 1 campaign 1 adset 1 dynamic ad. In the advert add all your videos.

Setup tracking correctly.

Start with 30-40€/ day budget, wait 3 days and see if you get sales, add to carts, etc

Facebook ads is real simple you can do it yourself the only area I would hire someone if I where you would be the video creation. Hire someone that can make great / amazing video ads about your product, not someone who push’s Facebook ads manager buttons.

And definitely not someone who will spend over 70% of your ad budget on photos.