The Brawler Fighter...is that just a Fighter with a gauntlet or is it something I can only build with online resources? In addition, is it a Fighter ONLY build, or would it work with something like Barbarian or another warrior class?
The Brawler fighter style is a Fighter talent (thus only open to full fighters) as opposed to the one and two handed weapon talents, tempest techniqe etc... Outside of the talent, which grants bonuses to unarmed and grabbing, there are a fighter powers that are based of having a melee weapon in one hand, and an empty hand in the other (including at-wills), you would need to be a fighter or a hybrid fighter to have access to those powers, though not nessecarily have the brawler talent
A spiked gauntlet is a simple weapon, otherwise. No other class I know of has powers tied to having a free empty hand.
All the info you would need is in Martial Power 2, since I read you don't have a DDI account, that is the book you would need access to for a brawler fighter. it contains the brawler fighter talent and all the powers related to that fighting style.