First, if you are in it only for the money, it's not worth it, just go merchant. I make around 500 coins for every rune ore I buy, and it depends how many rune ores you can get. You need to want 99 smithing, just because you want it.
For Who?
Not for the extremely rich, if you plan on spending 130m on smithing, just buy the steel bars, although it does take quite a while to get 99 smithing if your smithing purely steel bars-Not for any p2p noob.
If you are a 1337 merchant, just merchant than smith, merchant, smith, merchant, smith, merchant, smith and so on.
It is for the people that aren't very wealthy and who'd like to get closer to 99 smithing-Those that have patience
What you need
You need money to start you off, around 600k is good to start with, mine ores if really needed.
If you have somewhat a considerable amount of cash, don't bother mining ores.Just buy the ores so you won't waste time mining.
Purchasing Prices
These are the prices you should be paying, may change overtime.
Paying a bit more will get them faster, but go to high and you'll start losing money that could have been saved-if your paying to low it just going to take longer to buy them .
Cost per XP (smithing bars into plates)
What I'd like to do was determine on how much money 1 smithing exp would cost me, assuming we're always going to be making plates.
Do this because if you think you have enough cash to get to a certain level, like to level 85, you can check it by taking the cash your going to use and divide it by cost per XP and find out how much XP you will get from your cash you used.
Prices can change depending on how much you buy the bars for*also always take the market price of bars, never the cost it took you to make it, the profit/loss is yours when making the bar
Iron is the cheapest-steel is the fastest bars to get in quantity-mith is fast and somewhat cheap, but hard to find-addy is fast and a bit more expensive.
Example:If you have 10m, take 10m and divide it by price per XP for steel bars, 10.1, and you get 990,099, that number is the number of smithing XP you'll get when you use all of your 10m cash on steel bars
if your using iron bars, 10m / 7.6 = 1,315,789 XP-400k XP difference if your using 10m, but iron bars are slower.
Levels 1-29
Do the Knights sword quest, great smithing XP-Getting to level 30 should not be a problem, smith and smelt bronze or iron, buying bars is ok because it won't cost to much to get to level 30.
Levels 30-69
Buy a lot of coal and iron and smelt steel bars at Al Karid, try to buy in a 2:1 coal:iron ratio-Do not smith the bars or you will end up losing money, instead sell them at 550-600 ea at world 1, and try to sell in bulk-This method gets you: 7k smithing XP, and 40k an hour-With more money, increase the size of your stock and repeat-Smelting mith is not generally a good idea since it costs more to make the bars than to sell-Also while smelting, try to buy some steel bars from other smelters to merchant off them, you'll need the extra money.
Levels 70-84
Continue with smelting steel or - Buy the add ores and coal and smelt using the furnace, and sell the bars, it will be difficult to find an add bar buyer, super heating will cost to much-With the money you have gained off smelting steel bars, buy some bars to make it go faster, iron bars are better because they are cheaper waste (refer to cash per XP table).
Levels 85+
Should be a breeze now-Make and sell rune axes (slow XP but good cash)-Superheat rune bars and sell, or get someone like me to smith into better items-Do some rune super heating for people who are to lazy or can't do it themselves-At this point if you really want 99 smithing, with the profit you're making off the rune you can continue to smith iron to add plates until you reach 99 smithing, or you can get to 96 smithing and just make rune kites with stouts.
Opportunity Costs
Try to take the best path that suits you, and ask yourself could i have done something else? and analyze your choices and compare it to see which one is better-suppose you have steel bars waiting to be smithed, but since we know that the XP per bar is kind of high, sell them and buy iron bars instead, in the end you'll receive more smithing xp, but will spend a bit more time-time is still an important factor, smithing steel bars will save you more time than smithing iron bars, and the money you could have saved from the iron bars can be earned back when you make rune because you got their faster.
General Tips
Find something to do while smelting, talk to your friends, surf the web, do your homework, etc.-use smithing/smelting calculators on fan sites if your interested in knowing how close to are to the next lvl-use the Runescape forums or go to w1 fally east to buy and sell ores and bars-you have run, use it-do things in large scale, don't like make 100 steel bars than sell than buy 200 coal and 100 iron, do things in like 1000s-all smithing should be done at varr west, and smelting at Al karid.
I have probably told you nothing that you didn't know, that's how simple smithing is. It just takes a long time.
