well, imo
immortals items are better than tomeing
immortals items = 3-5 items + tetra essence + recipe cost
and the effects from the immo items are good too, ex. 100hp regen or 10k hp
some reg items i always keep slots for are the master ring or w/e and a staff of primarch
just for their windwalk and life steal abilities
ps. i almost never use tomes as it is almost always unnecessary