You have really asked two questions: best, most cost effective.
Just like with tools, you can go nuts and spend crazy amounts.
But, given your second question (cost effective) I am guessing you want to protect your home without spending a fortune.
If you are out in the boonies, I don't know that a camera system is worth the cost. I installed a wireless system from X10 on a previous residence and was impressed with how well it worked for the money.
You want a system that both calls the cops and sounds an alarm. The one I had would call up to three numbers, and it could tell if I answered the cell phone or if it went to voice mail. If it went to voice mail, then it called the second number and so on.
I don't believe I spent over $200. In conjunction, I also put up a few dummy security cameras. Crooks can't tell a real one from a fake one, and will normally just move on. They aren't in that business because they are industrious. They are looking for an easy score.
Hope this helps.