What are the most efficient uses for the first 100 gold that you get?

You can get a pirate realm key!

And you might be able to dye yourself a few times.

And that, is it.

I'd say don't bother.

Since you get most of the good stuff by looting there is nothing useful you could really buy for 100 gold.

Lately, if you had 100 gold, I would recommend you buy the backpack. It gives you another eight slots to hold items, which is pretty useful.

I used my 100 gold on a xp booster. it was worth it. I probably wouldnt spend it on dye because your probably going to want to use a different character soon or later, because if you do decide to use it on dye you lose your colour anyways when you change characters or die.