Check out the following articles. They show you how to get Ghost and WordPress running individually using the Nginx webserver. They should point you in the right direction:

• How To Host Ghost with Nginx on DigitalOcean

• How To Install WordPress with Nginx on Ubuntu 14.04

Putting them together, your Nginx configuration would look something like:

server {
        listen 80 default_server;
        root /var/www/html;
        index index.php index.html index.htm;
        server_name wordpress-blog-domain.com;

        location / {
                try_files $uri $uri/ /index.php?q=$uri&$args;
        }

        error_page 404 /404.html;

        error_page 500 502 503 504 /50x.html;
        location = /50x.html {
                root /usr/share/nginx/html;
        }

        location ~ \.php$ {
                try_files $uri =404;
                fastcgi_split_path_info ^(.+\.php)(/.+)$;
                fastcgi_pass unix:/var/run/php5-fpm.sock;
                fastcgi_index index.php;
                include fastcgi_params;
        }
}

server {                                                                         
    listen 80;                                                             
    server_name ghost-blog-domain.com ;                                      

    client_max_body_size 10M;

    location / {                                                             
            proxy_pass http://localhost:2368/;                               
            proxy_set_header Host $host;                                     
            proxy_buffering off;                                             
    }                                                                        
}

The port used for the proxy_pass should match the "port" setting in /var/www/ghost-blog-domain.com/ghost/config.js The server_name directive is also important here as it is how Nginx know how to correctly route requests.