As you have figured out so far, the best methods require experience and knowledge. But there are some rather easy methods. Those do not make you filthy rich. They can be done early and help you with a steady income until you are experienced enough to to for the real farming.
1.) Charged Quartz
It is one of the few daily crafts, which are very valuable. You need to obtain 25 Quartz Crystalsand interact with any Hero Challenge (glowing orb) to fuse them into a charged one. You can either buy those from the TP or farm them in the Dry Top& Crystal Oasis.
If you have Charged Quartz, you can craftPiece of Skyscale Foodin the Mystic Forge. You need Bloodstone Dust, which you gather on the go. Slabs of Red Meat, which you collect from killing animals or buy from TP. And Globs of Ectoplasm, which you obtain from salvaging rare & exotic gear. The final product can be sold on TP again.
The fewer ingredients you buy on TP, the more profit you gain from this method. Even if you have to buy the meat and globs, you still make some noticeable profit.
Note: Dry Top is a nice map to gather valuable materials in general. The Quartz nodes always are in the same locations. When walking to them, there are plenty of other nodes on the way. If you spend more time on that map, you also earn the map-currency. You can exchange it for 25Bricks of Clayand craft aClay Pot(Artificer 400, recipe from the same vendor). Which is also some good money.
2.) Iron Ore
This rather simple metal is a key ingredient in a lot of recipes, up to ascended gear. There is a huge demand for it. So this is still one of the easiest methods to make some pocket-money early in the game. All you have to do is gather the Iron Ore in the maps.
Iron Ore can be gathered in Brisban Wildlands, in the north-west corner at the canyon near Gallowfields Waypoint.
There is also plenty of it in the Gendarran Fields, near the mountains (both sides).
3.) Elder Wood
As you have a level 80 character, you can also go for the Elder Wood. While it is lower in price, you can farm more of this faster.
Best non-expansion/LW location still is the area west of Paggas Waypoint (bottom right corner) in Malchor's Leap.
4.) Silverwastes
If you have boosted a character, you know this place. It is one of the oldest and still most reliable farming maps in the game. Best method is to join an organized RIBA map on the LFG (= Central Tyria Squads). The system is rather simple. RIBA stands for Red-Indigo-Blue-Amber, the four camps in the map. You rotate through the map visiting those places, hit and run whatever you see. Make sure to participate in as many events as possible. You get a ton of loot in no time. Final boss and the 'chest runs' give even more loot. Just join the others and slowly learn how the map works. It is not difficult, but too much to explain in this little thread ;).
The map and its farming is also the perfect example to explain how most money in GW2 is made. Most of the loot you obtain there are containers, which generate random loot upon opening. You are supposed to salvage those items and sell the resulting materials on TP.
You can do this as a level 80 character and get acceptable money out of it. But if you ask people in the map, they may make double or triple of your income. The reason behind this mystery is, they use a bag opener. The level of the loot that drops from the containers depends on the level of the character which opens them. Upon salvaging the drops, you gain different materials. Materials from level 80 salvaging sell OK, but they are not at the peak.>Bag Opener level ranking for profit<
Once you have understood Silverwastes farming, you can get money out of most Open World activities easily. There are some maps that provide better loot than others. That map might not be the best, but it is the easiest for sure.
5.) Tequatl
Probably the most profitable Worldboss in Core Tyria. While the fight itself looks rather complicated, organized groups can make quick work of the dragon. I highly recommend using the >Event Timer<, which can also be opened remotely ingame via "/wiki et". There you can see all timed events and worldbosses in the game and when they are supposed to happen.
For Tequatl, it might be best to enter the Sparkfly Fen around 10 minutes before the worldboss spawns. Head to the LFG, World Boss section and join any organized squad.
If they are in another instance, just rightclick on any of the player squares in your squad menue and click on "Join Sparkfly Fen".
Tequatl loots gold, plenty of karma and containers.
