If Clomid is going to work for you, it is likely to do so within 3 cycles. The statistics are 80% in 3 cycles. BUT, that is for the women it works for. There are exceptions to every rule, I hate to say. There % is much lower for conception cycles 4-6. Some will still conceive during that timeframe, but much fewer.
Clomid is a pretty standard starting point and has been around forever. It used to be the only med out there and was just called "The Fertility Pill". It does work for most women that have trouble o'ing on their own. If it doesn't work(which it probably will) don't get discouraged. There are many other meds today to choose from.
I was on Clomid for three consective months last year while trying to get pregnant. I have endo and PCOS. I took a pill a day for 5 consecutive days a month. I was also monitored daily during this time by ultrasound. The clomid did seem to work pretty quickly. I had an average of three follicles every month released by my ovaries. I was unable to get pregnant on the clomid but it did produce follicles for me. My fertility dr later told me that clomid is usually the first med prescribed for fertility. I also didn't experience any side effects from the clomid, which was very nice. Hope this helps and good luck!