Name of the plugin you want :
ReferralSystemPro [1.8 - 1.12] Ultimate Referral System ! 1.2
Spigot Link :https://www.spigotmc.org/resources/referralsystempro-1-8-1-12-ultimate-referral-system.41294/
Price : 2.99 USD
How it would contribute towards the betterment of the community : it will help...