A website is quite a personal thing to you and your business. The look, feel and navigation of your websites will depend entirely on your purpose, so if you want to achieve direct sales via your site, you will need to have an eCommerce website that works well and where people can place orders straight away on your site. If you just want a website to make you look more professional, then you can have a more simple site, but it still need to be right.
You should discuss your needs and aims with your web marketing agency ahead of your website design and build. They can tell you about the different things that you can get out of a website, and what might suit you and your needs. Any good web design and marketing agency will be able to give you expert advice and help you arrive at the right decision.