Honestly if you don't have a lot of money to spend on a web design AND development (you'll need both) I would suggest using wordpress as a CMS and buying a nice decent theme from a site like
Themeforest. You could build one as well or modify the ones you see. I've do quite a bit of work in web development so let me know if you have any questions.
There are a few SEO plugins available with wordpress that will help you with that stuff but you will have to constantly maintain it as well.
Just curious, but what do you plan on budgeting for a designer, developer, and a SEO guru? Also find someone you know you can count or can contact in the future. I've had to help a few friends get things working once things break because they can't contact the original developer.
Get your social media accounts going and start interacting with your target audience while you're creating your site. Don't cross post and do those lame follow me type posts. If you interact properly and actually make meaningful posts while leveraging hashtags you're bound to make a web presence.
I'm a big fan of start ups so good luck!