Bookmark & use the following websites:

PoeCurrencybuy - the best palce to buy poe currency,poe Orbs,Exalted Orb and Chaos Orb.

PoE Wiki - Your place to go for any questions about the game, no matter if mechanics, item-related or whatever else.
PoeDB - Useful to look up datamined data such as enemy stats and stuff.
poe.trade - Most popular shop indexer, use it to buy gear or pricecheck rare gear.
Beware of price - fixers, always check for average prices instead of cheapest listings! currency.poe.trade - Same as above, but for currency trades.
poe.ninja - Use this site for pricechecks. Keep in mind that rolls can heavily affect the value of uniques with big variables.
Poelab - Shows the current Labyrinth layouts, services and other important stuff.
Exilemods - Great resource to look up possible affixes, ilvl requirements and roll ranges for gear.
Aura Planner - Helpful tool to work out your aura setup when creating a new build.
Vorici Calculator - Tells you the average of chroms needed to recolor your gear to desired colors.
Build List - Looking for a new build? This page will help you finding builds based on their main skill.
 

‣ Level gems: Make use of your secondary weapon slot to level a few copies of Arc and Storm Burst, or other popular gems to vaal or sell. Even if technically not active, these gems will gain experience. 

‣ Additional Guides: Engineering Eternity and Huizui are Youtube channels with video guides explaining different mechanics that are worth checking out!

‣ Don't give up: Path of Exile can be very harsh, even for people with experience in ARPG's. 
So don't give up if something seems too difficult or you made some mistakes, and rather try to learn from the situation.

‣ Have Fun: While Path of Exile has an overall great community, there are some black sheep who will ridicule anything that doesn't come up to their "efficiency standards". 
But seriously, screw all that. Having fun is all that should matter to you in a videogame, so play what and how you want!


‣ Use the help panel: This is a new feature that you can find on the lower right next to the shop button, and should be helpful with many different aspects of the game.

‣ Learn recipes: Path of Exile offers an extensive recipe system which you can use for your advantage - if you know all the good recipes.

‣ Level your masters: Elreon, Haku and Catarina can all substantially help you while gearing. Zana is very helpful once you hit endgame maps and should have a fixed spot in your hideout.

‣ Make use of crafting benches: After having unlocked masters by leveling them up once, you gain access to their crafting bench which you can place into your hideout.

‣ Use an item filter: You can find most relevant filters including a preview of each at Filterblast.

‣ Create a shop: Setting up a shop with Acquisition or through Premium Stash Tabs will help you selling stuff to buy upgrades for yourself.This little guide can help you to find out what gear is worth selling.