It depends. As of tomorrow’s update, gold will not be needed anymore for battles. So, going forward, you only need gold for three things: buying gold keys, leveling up your kingdoms, and contributing to guild tasks. Depending on what priorities you have, getting more souls or xp might become more important. All the armors are helpful to have, there is no doubt. But I just wanted to point out the change in case you hadn’t seen the post about it.
Edit: here is the official post talking about the gold cost change if you’re interested.