They could be anywhere throughout RuneScape.
You can wield a staff of earth, that way, you don't use earth runes for spells that require them.
read link below
Make runes. Air, Water,...
Check link below
go to every mage and fishing shop every day and buy all the water runes and earth runes and fethers
To get runes, you can either buy them from the various magic shops around Runescape, on the Grand Exchange, or make them from rune essence and pure essence at the runecrafting altars hidden around runescape. If you need help, my runescape username is Xeyran.
Operate you Earth Talisman which will guide you. Other than that it is not far south from the lumber yard. You will get there going out of the path of varrock tothe east and north
South of the monetary and west of Barbarian village.
Mostly Fire runes but Law runes and Air runes are not far behind them.
3 Water, 2 Earth and 1 mind rune
There is no cheat for Runescape, however the bestest way to make money is by Crafting Nature Runes.
You simply get some Rune Essence, and a tiara/talisman for the runes your creating ( depending on your level), then go to the appropriate altar and make runes.