[Messianic]

In case you havent narrowed it down, really the only spells which are research-only and you will actually use are as follows:

Pillar of Fire
Project Lightning
Enstill
Cast Force
Column of Lightning
Circle of Force
Thunderclap
Gravity Flux
Ice Comet
Paralyzing Earth
Supernova


Now, there are places which seem to drop more runes (and certain runes significantly more often) - although I have no data to back that up. Mammoths in EF drop tons of research components and the shaman spell vendor carries most level 20 and 24 runes. I researched all my spells in that level range using that vendor.

I found lots of level 24, 29, and 34 runes at the vendors all around the Felwithe Banker. They also seem to drop pretty frequently from Spectres (including level 39 and a few 44 runes, a single level 49 rune [impetus]), so anywhere a vendor is close to specs is a good bet (the magi pet spell vendor on AC isle and the vendors on sister isle in oot are good examples).