I'm currently making a minimum of 5k a day through Gem Sales.
Granted I spent time on my alt mining a shitload roughly a month before 5.4 came but if you put in the effort and maybe spend 3-5 hours 2 times a week you should be able to gather enough Ore to prospect.
Depending on Lotus sales on your server vs the Gem prices on your server, you may make a tidy profit from even buying the majority of the Lotus, to make Blue quality gems, from the AH but I went the extra mile and also spent time farming / using the Tiller farms on all alts and still do.
5k is a bare minimum, if I put some serious effort in, I've broke 40k a day through gems - Proof -
That's my way at least, another decent yield was 34k the other day -
There are many ways, this is just the way i do it