If someone had an idea for a coin with a purpose, where would be the best place to get help? If it's a good idea, that's just the beginning. Getting it done before someone else does it would be nice. That is assuming it hasn't been done. Who can keep up these days?
It depends on the nature of coin and the scale you want to go.
If the coins about some business, product or service, It would be better to collect the people specialized in the field from your local area. If you don't know any of them, starting from the local boards may help. Even a totally online global team could be possible but there would be many hurdles to it unless there's one leading person that specializes in almost every aspect of the coin and others acts in supporting role.