On your rune page, on the bottom left, there is a little button that kind of looks like a recycle button, that will lead you to the rune combiner. This guide is here to tell you how to get lots of rune for cheap, especially if you are newer to the game and have fewer (or no) full tier 3 rune sets.

Who will likely appreciate this guide?
New players who have read mobafire's guide on primary and secondary runes.
Players who don't have many tier 3 full rune sets.
Players who are interested in getting a lot of different runes.

The plan:
Buy 15 IP runes. Trade for tier 2 runes. Trade all secondary tier 2 runes for tier 3 runes. Eventually trade all tier 2 runes for tier 3 runes. (try not to buy full sets of tier 3 runes)

Pros:
Get a lot of different runes, especially good if you don't know what you want.
Way less expensive.
59% chance of primary or quint rune
Great for if you want to buy tier 1 runes, when you are low level.
Good for people with few runes and few full tier 3

sets.

Cons:
41% chance of secondary rune
You don't get to choose which runes you want.
Could get 10/4 of the same rune/quint, which you don't want.
Also you might get energy runes or mana runes, which are useful on very few champs.

First, if you don't know what runes are or what secondary and primary mean search this site and there is a good guide on that.

Next, how to use the combiner. If you own 5 tier 1 runes you can trade them in for a tier 2 rune. If you have 5 tier 2 runes you can trade it in for a tier 3 rune. If you have 2 tier 3 runes you can trade it in for a different tier 3 rune (I only recommend doing this if you have 10 or more of the same tier 3 rune). You can also trade in 2 tier 1 or 2 runes for a rune of the same tier, but I recommend never doing this.


There are 98 different runes:
40 secondary
30 quints
28 primary

The rune combiner claims that it gives a RANDOM rune, this means that you have a 58/98 chance of getting a quint or primary when using it.

So what I recommend you do is buy runes that cost 15 IP, and those only (unless their is a tier 3 set you know you really want). It will take 25 (cost 375 IP) to trade in for 5 tier 2 that will in turn be exchanged for a single tier 3 rune. There are 19 runes that cost 205, so odds are you will get more than you payed for. Also, the average cost of a rune is about 510 IP, so you are paying less than the average cost for a shot a nice rune.

If you buy ten runes (3750) IP you would expect to get 3 quints (probably 2 1025 IP quints and 1 2050 quint), which by themselves cost about 3840 (using the fact that average quint costs about 1280)

15 IP primary runes
Lesser Glyphs of Shielding (Mag Resist Per level),*
Lesser Seals of Replinishment (mana regen),
Lesser Seals of Clarity (Mana/5/lvl),
Lesser Seals of Resilience (Armor),*
Lesser Marks of Strength (AD),*
Lesser Glyph of Warding (MR).

*These are the most useful of the runes, in my opinion. (the mana regen ones are pretty useful too).

Unfortunately there are not too many good 15 IP Marks, if you want something more universally useful you could get secondary marks of resilience, warding, shielding, or replenishment.

Lets remember the plan:
Buy 15 IP runes above. Trade for tier 2 runes. Trade all secondary tier 2 runes for tier 3 runes. Eventually trade all tier 2 runes for tier 3 runes.

Lets assume you were just level 1 and just won your first game and you have about 240 IP and maybe 2 rune slots if you got to level 2. You have an open mark and seal spot. You can buy 16 runes. So you buy 9 AD Marks and 7 Armor Seals. Trade in 5 AD marks and 5 Armor seals. If you didn't get a decent tier 2 Seal or Mark and you really want to have all your slots filled, stop there. Otherwise, trade in 5 more and see what you get.

In case you skipped to this section and didn't read anything, here's the plan again:
Buy 15 IP runes. Trade for tier 2 runes. Trade all secondary tier 2 runes for tier 3 runes. Eventually trade all tier 2 runes for tier 3 runes. (try not to buy full sets of tier 3 runes)

When is it cost effective to trade in runes and when is it not? Since the average value of a rune is 510, it is cost effective to trade in a chunk of runes if they cost less than 510. The best thing to do is trade in 15 IP tier 1 runes, however, 2 tier 3 205 runes would still save you money, but you are wasting 30 IP, or 2/25 of a tier 3 rune. Anyway, the point is if you get 2 runes that cost 205 IP that you really don't want, trading them in is still likely to cause a net benefit, even though you have a 1/5 chance of ending up with a rune that cost 205 and a 2% chance of ending up with 1 of the 2 runes you started the trade with.

The plan:
Buy 15 IP runes. Trade for tier 2 runes. Trade all secondary tier 2 runes for tier 3 runes. Eventually trade all tier 2 runes for tier 3 runes. Its cheaper than buying (375 IP per tier 3 rune) most runes and a quick way to get some quints, but you don't get to pick.

Example of some combinations: My first 2 times I tried this I got a greater seal of replenishment (205 IP) and a greater quint of fortitude (2050 IP). Both useful runes, but I got ripped off on the first, but a fantastic deal on the second more than made up for it.

Anyway, this is one way to get lots of different runes for cheap. The only way to get more tier 3 runes faster is buy only runes that cost 205, but then this method is less efficient!