You should always aim for more spell power, no matter if you're leveling or are a end-game raider.
More INT means more spell critical, which is always nice, but it's not an important factor at low level, partly because you won't have enough INT for it to matter. Harder hitting spell power, however, always adds up to your spell damage, no matter how small.
The problem with spell power at low levels, however, is that it is very scarce. With the exception of a few quest items, finding items with +SP is difficult.
In principle, until AQ, you should prioritize stats something like this:
Spell power > Spell critical > Hit > Int > Stamina.