CSS and design work on established project

Hello, I have a site that I would like to further design into a service that can be sold. Currently, I do not charge users for registration and the site is monetized by Google Ads. I have traffic (50-100 visits per day currently) coming to the site but the ads are not generating profit. The site is [login to view URL] and its primary function is a web application that helps users create and manage disaster recovery and business continuity documentation. The web app is basically a multi-page form that dynamically updates a customers' database tables. The last page of the form creates a PDF document of the customers' information and saves itself to the database where it can be accessed from the users profile page. I designed the site in PHP and Javascript and it currently has 50 registered users. I have a solid understanding of PHP/mySQL and can work my way through Javascript but my design skills are limited/amateur and I'm lazy when it comes to CSS. What I would like to change: I like the layout of the pages but would like to add some more color/imagery and better more captivating front pages (index, about, contact). Not opposed to reskinning the site. There are currently 3 style sheets (root directory, user directory, app directory) and a few places where in-line styling is used. I'd like to combine all style sheets and remove the in-line styling. I'd would also like to start charging for the service. I would like a payment page that can process users' payments for a monthly recurring charge (settings stored in the db). I have a paypal account and wouldn't mind using them for merchant services. The web app is currently styled differently than the site which doesn't create good flow. I'd like the web app to look more like the rest of the site and contain navigation back to the rest of the site. I'm interested to hear any other comments or suggestions as well. I am not interestted in starting over with a whole new site or wrapping it with a CMS. I would like to augment the work I've already done.