Adding Dynamic Tools to a Web Project – Need Advice

I’m new here and exploring ways to enhance a personal web project I’m tinkering with. I’m interested in adding interactive features like real-time cost estimates, but I’m unsure how to integrate them effectively. I’m using Windows 11 on a standard hosting setup, with basic HTML/CSS knowledge. I’ve come across options like custom scripts or APIs, but I’d appreciate some guidance on the best approach.
Has anyone added similar dynamic tools to their projects? How did you handle performance or coding challenges? Any recommendations for tools or coding tips would be great.