Your optional subjects combination is fine, and there is nothing wrong with that...
plus if you want to apply online then you have to pay rupees three hundred via challan in favour of kpk psc, but if you buy form from NBP then you will pay three hundred rupees at the time of receiving form and there is no need of paying via challan/draft.
you need to submit character certificate received from your educational institution last attended plus character certificates from two responsible persons, who know you. responsible persons means gazetted officers/class 1 officers.
Regards