I'm never played PLD, but my main is WAR. I wouldn't worry about stance dancing in and out of sword oath and shield oath until you're more comfortable and familiar with the ins and outs of tanking. Even then, your best bet during normal trash is to keep your tank stance (shield oath) up so you're not as squishy and have an easier time holding aggro. I kinda cycle my defensive cds depending on the pull. Just don't use every single one of them at once because you don't want to go into another pull with no defensive cds available or have that pull last longer than expected and find yourself with no cds while all the dudes nom at your face.

When you reach 41, you can grind stone vigil w/ your squadron for gear, which will probably last you until you can get ironworks - or alternatively, just keep using the vendors. tbh, either option is fine.