I want custom angle grid lines.
i learned that i can make them act as guidelines, but how can i have grid lines other than vertical and horizontal gird lines ?
If you mean you want to rotate the Grid in Illustrator, as in
View > Show Grid, see Joojaa's answer - change the preferences for the Constrain Angle.
You can create guides at any angle though.,,,
Draw a rectangle the size of the overall grid you want....
With the rectangle selected, choose
Object > Path > Split Into Grid and define the divisions you desire.
Double-click the Rotate Tool in the Toolbar and input the angle you want. Click OK
View > Guides > Make Guides and the paths will be converted to guides.