Get either 30 Beenades or the Bee Gun or The Bee's Knees. Once you have any of those three (Bee GUn is the best though), you will be OP for the Wall of Flesh. Those weapons are the best for WoF, I can defeat him with that wearing no armor. As long as I have a clear path to run on.
The best gear is probably molten armor, but since it is a bit hard to craft it, i recommend shadow/crimtane armor... If you are struggling beating the WoF, try to craft some molotov cocktails. It's so overpowered to the boss, you can actually beat it easily with just a nick of time (i got this idea from Ningishu's yt vid: first night WoF killed)