Help improve shopify theme code

Job ID: 32772259

Budget: $50 – $0 AUD

I am building a shopify site and currently adding custom HTML, CSS and Javascript to the 2.0 DAWN theme. Because I am unfamiliar with the shopify json and liquid files I have been doing it by dropping custom html with inline <style> tags but I am ending up with a very messy page code with a lot of double up CSS and sometimes affecting other items.

I need someone that is very familiar with shopify to help me make the pages compleetly error-free and advise on the best way to properly integrate custom CSS and HTML into the shopify pages.

I had considered headless but I don't want to sign up for shopify plus at this stage.

Perhaps you could build a theme that allows easy insertion of custom code, I'm unsure how to best do this but willing to pay for an expert to advise and help.