List<Task> taskList = new List<Task>();
List<Staff__c > jobList = trigger.New;

List<GroupMember> GMlist = new List<GroupMember>();

for(Staff__c jobObj: jobList){
    if(jobObj.status == true){
        taskList.add(new Task(
            ActivityDate = Date.today(),
            WhatID = jobObj.Id,
            Status = 'Open',
            type = 'Other'
        ));
    }
}
insert taskList;