Trading

To get better items or better prices, trading with other players will be almost unavoidable. Here is the approximative values of some things.

Prices may vary daily, and some specific player profiles will pay much more for certain things.

World 1, Varrock marketplace
For some reason world 1 has more traders than any other world, excepting World 2's Falador Park. Varrock's marketplace has the most traders in f2p runescape.

World 1's Varrock marketplace is hard to work with because messages fly by way too fast; even ignoring the users who don't trade in what you need as fast as possible you almost can't cope with the newcomers!

Also, most people trade around the west bank. It is best to put your chat on HIDE when going into that area, as the text can overwhelm your screen.

World 1 varrock marketplace at peak time is a dreadful place to trade but near it (or at 5 am) is the best trading in runescape.

The general store in varrock world 1 can have goodies worth buying and reselling every minute as people lose patience with the flood of messages and the inability to locate potential trades first. Much can be bought there if you're not picky about buying random goodies to resell when you have a good stack of a certain goodie.

Gems and enchantable jewellery
Diamonds are worth 5k. Enchanted diamond amulets 6 to 10k.

Ruby is worth 1 to 2k. Enchanted ruby amulets are popular because they give a higher strength bonus (but no attack or defence) than an enchanted diamonds amulet.

Emerald and sapphires are worth about 1 or 2 coal (directly from another miner) or 200 to 400 gp each. Uncut are worth more because of the potential for XP.

The sapphire amulet of magic is worth 500 to 1k to someone who wants to start training magic.

Emerald amulets aren't very usefull or valuable, but emerald rings can be sold to members so they can make rings of dueling.

There is a good opportunity to raise your profit by selling a number of gold bars matching the number of gems you are selling, as well as balls of wool.

Shearing sheep
A newbie occupation, usually upon the request of a higher-level player. Unlike smiths, crafters have trouble coming up with enough gems to justify buying into balls of wool indefinitely so it's a one-day-only type job with only a small crafting exp gain.

Begging
Mining is faster money, believe me!

"Beggars are more hated than black dragons and evil chickens, and give less of a reward when killed."

About quantities
If you buy 12 coal from a fresh newbie for 1000 gold, you might have had an excellent price. But half the fresh newbies will expect you to walk a town and switch world every 3 minutes to buy another load of coal (mining it yourself is less hassle and faster). They also believe they can get anything they want from begging.

Experienced players trade most items in packs of 1000, it saves them tons of trading hassle. Reliable and hassle-free 1k traders quickly become popular and so can get somewhat better prices.

Patience is key.

About powerful players
A level 90+ smith may buy coal for higher than market price if you sell in chunks of 10,000. Very few players actually have the patience to accumulate that much, and the smith might be impressed. On the other hand they may have several mining clans already mining for them and ignore you as "one-time pocket change".

Smithing is the most gold per hour you can make as a free player, but it takes extremely long to actually turn a better-than-miner profit. Causal players should stick to something less demanding like mining iron.

Mining and smithing
If you're playing with close friends regularly, you can name one of them the smith and have everyone else be a specialist miner. This way the highly valuable smithing skill can raise to profit-making much faster! The smith however has a duty to share revenues with the clan so only close friends can be trusted for that; random clans met online may have the smith dropping the clan once he's rich and powerful.

Bronze, copper, tin, clay
Basically not worth the hassle of selling to players unless they ask for it (for quests).

Coal
150 to 200 coins each depending on the amount you're selling.

The most common job in f2p runescape is probably mining coal. There is no shortage of coal-buyers!

Steel bars
550-600 coins each depending on the amount you're selling.

Iron ore
100 to 110 each. As a buyer it's to have a steady supply as iron miners soon do coal instead - despite the fact it doesn't improve the miner's income as coal is twice as long to get and won't give them as much XP per hour as iron.

Extremely patient players have been known to mine only iron from level 15 to level 60, and then mine only mining guild coal (it's much faster) until they can make steel of all their iron. This trick saves about half the work you'll ever do as a miner up to level 60, time that can be counted in months!

Mithril ore
400 each. Varies a lot. You get a better price by trading the coal at the same time. This may have about the same value as bars because of the XP involved in making the bars being already taken away in bars.

Adamantite ore
900 to 1000 each. It is easier, but less profitable to smelt them into bars and sell them for 2 to 2.1k each.

Runite ore
11k gold each. Might be hard to find a buyer or a seller. Certainly worth buying when you see it in the general store!

Other runite miners are taking chances that an archer/mage entire clan attacking all at once and taking all their runite.

Free smithing
If you can't make your bars into the most money-making item possible, higher-level smiths might do it for you so they get the XP and you get extra gold (but no smithing XP).

Smelting
There is a living to be made by buying iron/coal to make steel bars and sell them. It's not certain of being more XP per hour than mining all and smithing all yourself, but the gold is better.

Rune essence
30 gp each. Members use it to make big expensive runes and may pay more if you sell them say next to where the law runes are made. If they run out of cash, try to trade their big expensive runes for 2 rune essences each. (-;

Since the introduction of pure essence, the above information is obsolete: Normal essence sells to free players for 10 gold each, pure essence is 80-90 depending on your seller.

There is a trick of going to the store, selling (stackable) rune essence note, buying the rune essence, and going to make more runes. In some rune places, this saves half your work time at a minimal cost.

If you go to world 16 air alter, there is a air crafting company there. they should buy your ess for 20 to 40 gp each

Leather
You can trade 25 cow hides for 12 to 15 ready-to-craft cow hide from someone high enough level to enter the crafting guild. Cows are nearby and you just have to pick cow hides off the ground. Both players will gain XP quicker this way.

Pottery
Rarely a cook will order 200 bowls or 200 pots or 200 dishes. If you have no crafting XP anyhow and no good income source this is a good deal since otherwise you won't make profit over the pottery you make and you'll have to make some anyhow to get to better crafts.

Jewelry
Players don't buy free player jewelry items unless they want something enchanted; that's because those items lack the quality of being rare. Don't waste time trading in those nonenchantable types with players.

Silver, gold ores and bars
Silver bars are worth a lot to someone who wants to raise his crafting skill. Crafters also need gold ores/bars so they can make jewelry. They won't however buy more than 100 or 200 gold bars at a time unless you have a matching number of gems with it!!

Food
Any food becomes more valuable when far from the bank and into dangerous areas. Players are literally dying to buy it, and in the wilderness they may kill you for your food as a survival strategy rather than buy so be careful!

Fishing
Raw or cooked lobsters: 200-250 each

Feathers
Feathers are worth about 10gp each because of fishing and arrow-making. If you don't need them it's good to keep them for fishing later as it's faster to raise skill feather-fishing than any other way.

Bones
Bones - 10gp each. Big bones - 300 to 350 gp each.

Runes
Elemental runes: 15 gp each.

Law: 300-350 each.

Nature: about 300 each. A timesaver for smithing high-end ores on the spot and high alchemy stuff rather than bother selling to players.

Chaos: about 100 to 150 each

Death: 250 to 300 each

Body: 5 to 10 each if you can finda buyer.

Masks
(Removed because it was incorrect)

Party hats
Worth 110 to 310 million coins depending on the color. The ultimate status symbol and investment.

Members items
Some items are so rare or long to make or both they are worth millions.

Quest items
If you have 10+ items an experienced player starting a new character might pay 1000 gp each for saving half the hassle of questing all at once. However waiting for such a player takes a long time and your bank tends to get annoyingly full with quest junk so it's not worth it if no one requested that in advance.

Woodcutting
Yew logs are worth 250 each to members who make bows.

Walking
There are a lot of situations a skilled player want to stay close to a skill-gaining or gold-gaining place and have newbies do all the walking for them.

Convenience
If you're quick, trade exactly the full list of what the other wants, and then never nag your income will increase marginally from people prefering to deal with you. At very high smithing levels the smith can afford to trade only with the nicest people when faced with equal prices and quantities - they might even have chat permanently turned off for people they didn't find nice during their skill acension! So be nice and convenient it pays.

Cooking
Buying cakes and adding chocolate powder to get chocolate cake is a very quick money maker for two cooks of uneven level to make.

Slavery
Some people will sell a specific number of hours of their work - at anything the buyer wants the slave to work - to fill gaps of hard to find items (i.e. get more iron for you when you mine the coal to make steel; gather cake ingredients; gather 10+ quest items for you; etc).

The jaw-dropping extreme is the members having newbie members buy potion containers full of water at 200k for 1k containers. You might even have the job of merely filling the containers with water!!

Novelties
Any new item introduced by jagex might become ridiculously overvalued for a short while as many players don't know where to buy/find/make it. For example I paid 2400 gp for a sleeping bag worth about 35 at the general store in my first ever runescape week. (-;