I am in need of advice as well. playing a zealot Barbarian, 18 STR, 14 CON and DEX, 10 everything else, already have GWM, and using a glaive for my weapon. And currently wearing Scale Mail given by my character's benefactor. Almost at level 8, and my options for now seem to be:

1. Bump STR to 20.
2. Bump DEX to 16. Extra AC, better initiative, better DEX save
3. Bump CON to 16. Extra HP, better DEX save
4. Take Polearm Master because...Polearm Master?