To add an Image Gallery to Ghost Blog, you can follow these.
#Option 1. Use Gallery Widget
#1. In the post, click where you want to add and Enter . Then click + symbol and choose Gallery
#2. Click the box to select your images then click Update
#3. Result
#Option 2. Use Tool
#1. Access this link and click Create Widget for Free
#2. Choose your desired layout and click Continue with this template
#3. Click Add photos to add your images and Heading to enter your content then click Add to website for free
#4. Click Publish
#5. Choose Free Plan then click Copy code
#6. In the post, click where you want to add and Enter . Then click + symbol and choose HTML
#7. Paste the code and click Update
#8. Result