Low level PFS items

Hi everyone, recently I got my first Pathfinder Society character up to level two. Character is a Fighter. I now have some gold leftover after the weapon, shield and armor I wanted, and am not sure what else to spend it on. I've managed quite well so far with character options, but items seem significantly harder, especially because I am bound by PFS rules to only use items I have source books for (i.e. mostly just core).

Any suggestions what I should be on the lookout for now and the coming levels?

P.S. is upgrading my Steel Shield to a Tower Shield worth it? They seem functionally identical (Unburdened Iron Dwarf) other than the ability to take cover, but that would cost so many actions in total I'm not sure I would use it often.