So I'm in a party of 6 PC just starting the Dragons of Icespire peak. I'm going to be the party tank. I'm playing for theme and battlefield control not min/max damage. I'm a varient Human with Shieldmaster at first level, will be going Path of the Zealot at 3. 

So ASI to STR at 4 for more damage/hit and better Athletics for knockdowns, ASI to CON for more AC, HP and Con Save or Take Sentinel feat and work on locking down the battlefield.

Out of curiosity, If you're planning on being a tank for battlefield control, why not choose Path of the Ancestral Guardians? Thematically it seems to make more sense than Zealot. 

To be on topic, being a shield master barb, your AC is already going to be higher than other barbs at your level. the extra point in AC may not be worth it over battlefield control. Could you show your character sheet or give your stat-line or something so we have a basis to go off of? 

Role playing and want to do a bit more damage with Divine Fury. Freed slave liberated by followers of Hoar, will be using his skills to be a bounty killer.

Character Sheet

I would get a feel for how the character plays the first 3 levels.  Do you feel like you're missing too much when attacking?  Take the STR ASI.  Are enemies running running away from you even when you recklessly attack?  Go for Sentinel.

I wouldn't take CON (for now) since Zealot's raise dead ability lessens the sting of dropping to 0 HP.

I play a tank Barbarian (with a few levels in Warlock) and I use Sentinel. I may take the time to unlearn it and go ASI though because stuff is starting to hit harder. I've already ditched a second weapon for a shield so im up to 18 AC. I just dont get to use Sentinel enough. Part of that is our rogue stopped playing and she was the only other melee character. So the rest of my party is at range unless the Cleric goes in for an Inflict Wounds. But when we did have the rogue most of the enemies were focused on me.

I'm in the camp for taking AG instead of zealot. There are other ways to get extra damage (which isn't the goal of tanks anyway) and AG is tanky as crap especially if you reckless attack. If you anticipate high levels, you'll get some extra damage at 14th also. If you want to tank, take tough for the vhuman feat, go AG and at 4th take ASI CON. If you really want the damage output forget shield master and take GWM then at 4th take PAM but that's not being a tank. 

With AG the first attack doesn't have to be melee. So you can protect an ally by throwing a weapon and then get between them.