Buy your armor FIRST, if you can wear armor at all. Then you can worry about weapons and other gear. Upgrade whenever you can.
Use those healing items. They are generally very, very plentiful and you can carry 99 of them with no penalty (Secret of Mana being a notable exception).
A single night’s sleep is often all you need to heal from almost any wound, even nearly fatal ones. Broken bones knit overnight, the poison/radiation wears off, etc.
When in doubt, grind. And search every kill. Try to skin every kill, too, if you are capable of this. Even non-sentient monsters will occasionally carry items, mostly the local currency, as Martini Enfield notes, but sometimes rare magic items. Just…don’t ask WHERE they were keeping these things.
Many times, the only way to get certain items is to steal them. Either you can’t buy them at all, or they are rarely for sale. So, limber up those fingers, keep your lockpicks well oiled, and save before you steal. Sometimes you can even steal DURING BATTLE! Damn, you’re good. And if you turn around and sell that rare, valuable (but useless to you) item to the shopkeeper you just stole it from, he won’t question where you got it! Stealing almost never affects your alignment, either. If YOU’RE doing it, it’s because it’s for the greater good. So the only thing you should worry about when stealing is whether or not you can carry it.
When playing in meatspace with a human DM, bribes to the DM are almost always accepted. If the DM is fair, s/he won’t let bribes affect your character. But s/he’ll accept the bribes. I have found that homemade food is particularly welcomed. I find that lasagna is very popular, as are most cookies. Do try to find out if someone keeps kosher or otherwise has dietary restrictions, though. If you collect money in order to pay for ingredients or a run to the border, the group should chip in for the DM’s share.