Yes and no. You will increase the number of runes you create per essence as you level up, but it does not change on every single level. For example, you will create one air rune per essence at level 1, two per essence when you reach level 11, three per essence at level 22, four at 33, five at 44, and so on. Also, some runes cannot be created in multiples no matter what level you reach, namely Law, Death, and Blood runes.
You need level 14 runecrafting to make fire runes.
You will need 20,267 Air Runes form level 1 - 50 RC, so I'd say that amount in Ess.
Pure essence can be made into high-level runes with the runecrafting skill.
you make them with the runecrafting skill
about 70-100 days when you have got the level for nature runes
earth or fire cause they are very close to banks
You need level 15 runecrafting Have in your invent Fire runes and talisman or Air runes and talisman and pure essence. If you have fire runes go to the air alter, if you have air runes go to the fire alter then simply use the talisman on the alter. There is only a 50% of success, i recomend wearing a binding necklace to increase this to 100%.
Make runes. Air, Water,...
Runecrafting the runes is your best bet, or buying the runes from GE, players or Ned in Varrock.
crafting runes at alters. Use runes ess at certain alter to craft those runes. Eg water alter you crft water runes.
You can buy them at the Grand Exchange - or make your own, once you have the Runecrafting level.
The fastest way of getting RuneCrafting up is to make special tiaras - air tiaras, body tiaras, etc. As with many other skills in RuneScape, the fastest way is also the most expensive way. Making runes you can earn money (at least with air runes, and with some runes that can be made only by members); making the tiaras, you actually lose money.