[lasre]

> Turning still images into GIFs

Using a file converter will probably do the trick. There are also GIF-making websites that allow for more customization.

> Adding effects to a GIF

The simple method would be to find an image editing website and simply apply an animated effect to the image - e.g overlaying a gif of sparkles.

The other option is to convert the GIF into a video file and use video editing software - this is probably overkill, but does give you more options.