In addition to what ualaa said: (and listening to him can never be bad :P )

During the latest weeks i only put out a couple of gems/cuts per day on the AH during the week. I just stack them for the weekends. Prices seem to be sky high on saturday/sunday morning/afternoon. And by flooding the market with 60 gems at once, 1% under the lowest AH price, they sell like candy (stacks of 5 & 10 works best for me).

i can do 3 cuts: runed cardinal ruby, bold cardinal ruby & solid majestic zircom. My rule of thumb is to have max 10 of each kind (both listed and in the bank). Any raw blue/reds I have extra, i just sell them uncut. This to avoid having too much in stock.