What is the best way to make a gif to post on tumblr?

[Nightsanity]

The pictures have to be the same size in height & width for best results.

Use lunapic:
http://www133.lunapic.com/editor/

This will allow you to edit,resize or crop if necessary.

1.Click browse to load the image

2. Select scale to resize if you need to. you will have to make all pictures the same size.
once scaled to your linking save each image in it's new size.

3.Click on Animation in the top Menu bar and select add animation frame
browse for your picture and set the speed you can use .1 for very fast then upload.

Just repeat the process of adding animation frame, selecting the picture and setting the speed.

4. Once your gif is created and you like it save it and upload to an image hosting site.
http://imgur.com/