Thank you Danubian, Wargasm and Einar for your advice.
I will mark this tread as favorite. As there is a lot of info i can`t absorb after reading it once or twice.
Hope this will help some new players as well. It has been helpfull to me.
Now i know what i need to know about ammunition. And i better build up to 12 mercenaries. I used to stick with 6 for a long time.