Here's two strategy games that help In Seega, your objective is to capture your opponents marble by sandwiching it between 2 of your marbles. A good game that makes requires players to plan 3-4 moves in advance.
The objective of 9 Man Morris is to make a Mill or 3 in a row (horizontally, vertically or diagonally) while trying to prevent your opponent from making a Mill. When you make a mill, you get to remove one of your opponents marbles from the board.
Two games of strategy for ages 6 and up. This game folds up with all the marbles stored inside.   Comes with 24 marbles and instructions for both games.