Step 1: Identify the core problem in PCOS-related infertility, which is failure to ovulate. Fixing fertility here means kick-starting ovulation.
Step 2: Clomiphene citrate fits this need. As an anti-estrogen at the hypothalamus, it tricks the brain into sensing low estrogen, which boosts the pituitary release of FSH and LH and drives a follicle to mature and release an egg.
Step 3: Its oral route, low cost and good ovulation rates make it the standard opening drug once weight loss and lifestyle steps are addressed.
Step 4: The remaining options - injectable FSH, GnRH and assisted reproduction like IVF - are second or third line steps used only when clomiphene fails. So the first line choice is clomiphene.
\[\boxed{\text{Clomiphene}}\]