Wow, I'm at about 1200 amber and 400 citrines used, but only 65 imbuing. I know obviously ROT makes it much easier, but I wonder what I'm doing wrong. Total cost right now is about 200k, but that also includes about 300-400 amber/citrines I still have left in the bank for training.
Very similar situation, I spent 300k on gems and I am at 77 imbue with lots of gems left. Once you hit ROT some light farming of gargoyles is all thats needed for the gems ( they drop 2 - 4 per kill, and the shadow gargoyles in the Kings Tomb are even easier to kill! )
I could have gotten away with 200k total for training purposes, and farm the rest at ROT up to 120 skill.
The techique I use only uses 1 gem per imbue attempt, not sure what everyone else is using.
Start with a exceptionally crafted dagger ( which starts with weight if you need higher difficulty ) or tinkered butchers knives, if you dont need the raised difficulty of exceptionally crafted, stone a skill and make regular.
I am using amber and saphires ( because I have many of them ), I imbue hit cold on an item, then switch to hit dispel using amber, the weight from increased damage from exceptionally crafted plus the increased weight from hit cold will increase the difficulty enough to make it only require one gem for the last nine gains on that dagger. Once you hit ROT, you'll be only spending 10 - 13 gems per 1.0 gained.