When choosing a responsive theme for Shopify, it is important to consider the following factors:

• The type of store you are running: Some themes are better suited for specific types of stores, such as fashion stores or electronics stores.
• The features you need: Some themes come with a wider range of features than others, so it is important to choose a theme that has the features you need.
• The design you want: Some themes have a more modern or traditional design, so it is important to choose a theme that has the design you want.
• The price: Some themes are more expensive than others, so it is important to choose a theme that fits your budget.

For most first-time Shopify stores, it makes the most sense to start learning about Shopify using a free theme. Once you have the hang of the Shopify store setup, you can purchase a theme from either the Shopify Theme Store or a third-party theme store like Envato Marketplace.