First process that is to be followed by any site is on page than you can switch to off page.

Both are important on page and off page seo

Both offpage and onpage process are must for to do seo.

Off page optimization is more time consuming process and it can't be done in few
hours or days.

Offpage and onpage submissions are best for traffic.

without ON Page And Off Page, get good ranking is not possible, so Both are very emportant techniques in seo.

Onpage:

Keyword in title, description, page content, image name & image alt text.

Offpage:

High PR relevant backlinks that you can build yourself or purchase from quality vendors.

On page SEO and Off page SEO both are useful for getting traffic to your website on a page helps to increase your website quality as well as off page is good for getting traffic.both processes are must for getting high page ranking.