Gradients, as many resources in Illustrator, can be used with the repeat feature and used to great effect. You can use the linear as well as the radial as well as freeform with the feature. You can use it with the three options, radial as well as grid and mirror
You can find it near the bottom of the object menu
Select an object or multiple objects. Apply the effect. You can modify the spacing of the repeat object, the instances and more and it is all a live effect that can be changed over and over to create the most amazing designs
The Radial feature works well with gradients but it should be noted that thy are not blended, they are always separate objects so you will see some slightly ungainly overlaps if you push the effect too far. Select a design filled with radial or linear or freeform and then go to the object menu and repeat and radial. You will then see the default number of instances of the filled path (or multiple filled paths). You can increase the radius as well as the instances via the object. You can also double click any of the objects in the radial object and then you will find that you are in isolation mode. Inside isolation mode, you can select the tool and then edit the preset such as increasing the diameter of the radius or moving the origin. You can always right click and use the exit editing mode / isolation.
In isolation mode, you can also go to the gradients panel (find that via the window menu) and you can change the stops as well as the type such as setting it to linear or freeform etc. Any changes to one of the presets will be modified in all of the other identical designs. Once you are finished with your editing of the object, go to the top left and exit isolation mode. You can then continue to change the number of instances as well as the radius and size of the overall container object.
You can increase the number of instances to create intense lines of the selected object. You cannot change the colors etc of the object until you enter the editing mode. If you use grid mode then you can also edit the objects (via isolation mode) as well as freeform, radial etc, you can do this by double clicking the item. The object you have selected will be highlighted and all the other instances will be less visible. Once you change one, all of the designs will be update with the new shape etc
You can also use the feature with mirror by selecting a path and then go to the object menu as with the others. The path can be separate or melded to the mirror design depending on the dividing line position. You can edit this dividing line at any point and when you change it, you will notice the other side of change as well. You can also double click the repeat object path (left side path is used for the editing) and then edit the artwork in isolation mode and change the color from linear to freeform or linear to radial etc.You can also create a mirror artwork with and still it is editable and live. You can also add a radial to the mirror. You can also add additional paths to the object at any point.
Mirror, Youtube video on subject
You can apply it more than once. Select an object filled with linear / radial / freeform. Go to the object menu and apply one of the approaches (radial, grid etc) and with that object selected, change the radius and instances. With that selected, go to the object menu and then use the radial / grid / mirror again. You can do this multiple times but the result can eventually be messy. Probably works best when you combine a grid with the circular object or the mirror with the circular etc but sometimes multiple circular live designs can result in a bit of a mess depending on the initial object. There is a certain point where this will cease to work.
If you have the Astute Graphics set of plugins, you can always double click an entry and then apply the plugin Randomino and re-color all the stops to create all kinds of amazing artwork. You need to enter the editing mode before you can apply any others as well
Edit the design by double clicking an entry and then with that selected, go to the edit menu and recolor artwork and you can then re-color any of the stops of your design to create all kinds of color variations. You can also use the swatches feature so you can then select different libraries of swatches on the current selected preset.