From my experience I would not advise you to go with Venture Capital when you're a start-up as in the end they will most likely end up screwing you. A much better source for funding would be angel investors or friends/family.
The question of how much equity should I give away differs for every start-up. I remember with my first company I gave away 30% because I wanted to get it off the ground. This was the best decision I ever made. Don't over valuate your company as having 70% of something is big is a whole lot better than having 100% of something small. You have to decide your companies value based on Assets/I.P(Intellectual Property)/Projections.
I assume you have some follow up questions and I would love to help you so if you need any help feel free to call me.

Kind Regards,
Giuliano