You should be able to get to ilvl 55 pretty easily with the GC gear. I remember that's what I bought when i reached 50 to boost my ilvl high enough to do the relic quest. After that you can upgrade your relic to ilvl90 and then you can start doing ilvl60 dungeons and work your way up... the transition is pretty smooth already I think. You have dungeons that drop ilvl55, ilvl60, 70, 80, 90 and 100.