I'd say 3 months into applying the DJ bible actively, having completed DJ bootcamp or something like it, and actually BEING a DJ day in and day out, getting 12-15 numbers a month is not unreasonable, and for some may even be on the lower end.
I can testify to having seen a DJ buddy of mine who also posts here, MiggityMike, get that many numbers, and have several successful dates following.
I myself have had similar success. I am not using any secrets that cannot be found in the DJ bible.
I'd recommend any aspiring DJ to focus on consistency. Consistently being on top of your game is highly important. One day as a DJ is nothing compared to one week, and one week as a DJ is nothing compared to embodying the DJ for a full month. Now imagine 6 months or a year.... Start with a full day, work to a full week, aim for a full month, etc.