You may want to check with your state associations. Often times they can offer you a sanctioned event as long as all participants are members of that association. A sanctioned event will allow you to use that associations insurance. It is possible to get private insurance as well.
You'll also want to contact your local dealers and shops to start bringing in sponsorship in the form of money, prizes, equipment, otherwise.
You'll need options for judging, will it be a riders judged event? Will you bring in certified judges?
Will this be a large enough even to warrant bringing in outside medical or security? Will it be small enough that designated volunteers with up to date first aid and cpr can cover it?
Where is your venue? Do you need any state permits or local permissions? Are people coming in from out of town? Do they have accommodations available? Camping? Hotels? Will a host city/town join in the sponsorship bid if the event is big enough to bring in tourism and spending?
Do you need an announcer? Other activities? Vendor space?
You can do this as small as you want or as big as you want. I've given you ideas to think about from the small to the big. I've been involved in wakeboard tournaments and events from 10-50 people (the norm) and to an extent 150-200 people.