@taimurshoaib I may be wrong here but you may be going about this a bit backwards. There are regular themes in RW (like WordPress) where you can “tweak” the theme itself but, overall, need to live with the theme’s look and feel.
In the Rapidweaver world there are also things like WP page builders (think Elementor or Divi for WP). These are not pre-formatted themes per se. Instead they let you build your own theme/look. Foundation, uiKit, Foundry, and Platform are all examples of “page builders”: they are tools for building your own theme.
From your initial post it sounds like you don’t want to create the theme (or “look and feel”) yourself, but to only add content. If that’s still the case then you need to first find someone willing to duplicate your current theme. (BTW the theme may not be able to be exactly duplicated, but in large part it can look similar.) So it’s finding that “someone” first. Then find out which tool they want to use as they will have a preference. That preference, in the end, is what you want to purchase.
If I’m wrong, or if you’ve changed your mind and what to duplicate the theme yourself, then there are still the options listed above. In that case I’d probably suggest looking into Foundry and/or Platform. They are both more accessible to newbies. If you do have a background in design a bit then UIKit might be a wonderful option (I’ve only heard great things about it but haven’t used myself).