I made 120 towards the end of last month, using monster loot only. After a while you can more or less figure out what items you can gain from so you don't have to examine every item.
Up to around 100 I gained around 5 whole points every day, from then on it dropped to around 2 full points each day (one session using the 8 or 9 bags of loot, around 60 pieces each bag, that I collected each day).
From 110-120 I dropped to around 1.5 full points each day, although you have to spread your imbuing range from 45-70% (sometimes doing the odd essence imbue) otherwise you won't do enough imbues. From just above GM onwards I was more or less residue neutral, meaning that I never used up any of my existing stock but used those from my daily loot bags. As for gem usage, I would always take it up to 3 gems, then back one click, so would always use 2.
I think that the key is to do as many imbues as possible, so spread your percentage range (45-70) and pause when you get failures, don't start hammering away at the imbue button. I generally had strings of successful imbues because I waited for the sound to stop before I imbued again.
In general I would say that I had many more successes than failures, because I didn't rush it.
At 119 I gained three times off two successive items, at around 71%.
Three times I never failed on an item, and I got three gains from the 11th imbue, so it is quirky. Most of my multiple gains from one item came in the 45-50% range.
