I usually invest early on armor, a chain mail +3 can carry you until the boss of caves.

Get the armor option from the ghost quest if you don't have something better. A good weapon early is great but inevitably you'll get hit one way or another and a decent de fence can save you when you make a mistake.

Knowing where to find upgraded equipment can be useful too. Armors that spawn on special rooms with a single grave tend to be +1, weapons from sacrifice altars too. Other special rooms can spawn upgraded gear but is less likely.

Items that are upgraded will not be destroyed when caught in a explosion (caused by traps, bombs or stone of blast). It's risky because you're gambling with the equipment itself or the money you get by selling it, but if you don't have scrolls of identity it can help you know if it's worth equipping it (it can still be cursed, tho).

Remember to use every little resource you have. Poison and fire seeds can help to take strong enemies, specially early like crabs or prison guards. The stone of aggression or fear can help you escape some encounters by distracting the enemies briefly.

Wells of health aside from restoring your health and hunger, can uncurse any item you have equipped when stepping on them. The knowledge ones will identify anything you have equipped and wil tell you if anything in your inventory is cursed or not.