It is easily achieved from Admin, I assume you have already created theme.
Most of the one confused after creating new theme they lost home page look and feel because home blocks are not assigned to the home page while we create new theme. We only do it manually.
please follow the instruction
login to admin, then navigate to
Conten -> Pages
find Home Page, then in action column click edit then
click the Content tab then place the below value in text area
{{block class="Magento\Cms\Block\Block" block_id="home-page-block"}}
note: here block_id is unique id of blocks, you could found the list blocks and block id under Content->Blocks
finally save page
then clear your cache of magento and browser, load the home page, you could see the home page look like luma home page.
if you want to find home page html content, find block home-page-block under the Content->Blocks then edit the block, you could see the html content of home page.
take the reference of this html conetent, after that you can develop your own html as per your requirement, Add CSS from your theme layout file.
you need any clarification just mention in comment
have good luck.