You can pretty much ignore white items unless you're about to go back to town and have the room to spare for them. Rarer items are often worth picking up and selling, even if you have to hold onto them for a while. And of course, any item that appears better than your existing gear is well worth catching -- even in the event that you need to lose something else temporarily as you equip it.
By default, characters do not regenerate life but they do regenerate a very small quantity of mana every second. You are able to manually refill life and mana by using the proper kind of flask. Flask charges automatically refill when seeing a city or hideout. They also gain charges from killing enemies. Equipping better flasks raises the amount of life or mana regained, and can have other effects as well.
Gear and passive abilities can increase regeneration for either stat or even steal life and mana from strikes and kills. At bare minimum, you would like to have some life regeneration so it is possible to recover health between conflicts.
These hints should start you on the path towards returning home and exacting revenge on people who exiled you. One more tip to consider: if you're fighting with the POE game solo, you can usually invite a friend or Path of Exile participant from city to assist. Don't take your exile sitting down!
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