I have multiple gmail accounts on my phone. I only want 1 account to sync contacts. I know how to stop it from syncing contacts in the future but I do not know how to stop it from syncing the contacts when adding the G-mail account originally.
You can simply deactivate automatic synchronization on your device; when you add a new Gmail account, contacts won't be synchronized. If then you want to synchronize your contacts for one account, you can go into your device settings ("Account" section) and activate synchronization for that account.
For example, I have a Huawei Y560, and I have to go to Settings --> Account --> Google, then choose the account; there will appear a list of options that I can synchronize just clicking on.
Otherwise, you can also activate synchronization for one account via Gmail app ticking the related voice in settings.