I was wondering if there is any firewall for MyBB, I think there is but I do not know.
You don't need a firewall for MyBB. You need a server firewall. If you're on a shared host, this is taken care of for you.
I am planning to buy a VPS and might need support, maybe Omniscient could help me.
Get a managed VPS if you need help. It will come with iptables and a firewall config in your control panel.
Hmm, thanks for the suggestion. I will do so.