buy runes first. Try to get these, pretty decent enough for about everyone:
Purple and Red:
If you play more AP:
flat AP quints
magic pen reds
If you play more AD:
AD or armor pen quints
armor pen or AD reds
Alternatively, you could get movement speed quints, works well on just about everyone.
Blue:
flat magic resist blue on everyone
Yellow:
yellows kinda suck. You could get dodge (expensive) or mana regen/level or HP regen/lvl
If you want to jungle all the time swap for these instead:
armor yellow (most important)
magic resist/lvl (instead of flat) blue
attack speed red for most junglers
don't get movement speed quints
Some characters are more specialized (ie, jax you want to spam AD runes and dodge runes, Akali you want to do whatever double passive lvl 1 thing, vlad you want HP HP HP, etc)
Once you have a set of runes or two that lets you cover almost everyone pretty well, you can start buying champions until you feel the need to made a specialized rune set for a specific guy. Alternatively, buy one or two champions (I bought Ezreal and Warwick first thing), then make a rune page that works well with him, and play him 24/7 until you have tons of IP. Granted the reason this worked is because jungle Warwick is incredibly OP at low level play and you just nonstop win until your hidden normal ELO is super high.
My normal game play % is probably something like 85% Jungle (most of which is Nocturne/Warwick), 5% Ezreal, 5% Singed, 5% all others. I can basically get away with one page for noc/ww, one for ezreal, and one for everyone else.
Give us a visit and have fun 
