High enough is whatever you think you need.

Skills just make the game easier. Some might also say more fun, at least when it comes to stamina drain, and that is at least somewhat valid for skills like running and jumping, but the primary effect is that it lowers your stats in several ways, which means you have to hit more, track stamina more closely, run slower, etc.

I worked my way to mistlands the first time swinging a sword, and then switched to frostner, and added an atgier soon after, both with 0 skill to start, and did okay. I'm sure it would have been easier with higher skill, but is easy the primary goal in this game?