Hello Joaquin, following the examples:

pessoal = folks

gente = people Ex.: Havia muita gente na fila "There were a lot of people standing in the line"

pessoais = Ex.: Problemas pessoais "Personal problems"

pessoa = person Ex.: Ele é uma boa pessoa! "He is a good person"

so, I'll explain in the point of view of Brazil

personal = staff or people such as: this is my personal from my store;

gente: people, used to identify a group of people, at work, friends, family

personal: I do not know this word, it is not used in my state

pessoa; person, it is in the singular ... all the others are in plural

Hope this helpe you

sorry for my English