Convert our custom built blog into a WP theme

We have a custom built blog which we made ourselves. It's PHP and CSS based and we need someone to convert it to a Wordpress theme. The site is currently responsive to the theme needs to be too please. We are very happy with the design although there might be a couple of small tweaks here and there so we'd like it to look the same please - [login to view URL] Question: we have two types of categories currently. We can say that a post is an article/video/product update and if you look on [login to view URL] on the right, you can see things like ‘automated income’, ‘automated marketing’ etc. The reason we are switching to WP is for SEO purposes as WP blogs get ranked way higher than custom ones by default. How do you suggest we work this? One could be categories and another one could be tags but what is best for SEO? Happy to answer any questions and I can write up some notes on each page but it should be fairly obvious what needs to be done. It all needs to be as editable and fluid as possible please.