well i’ll try and give my best advice, cause im definitely no expert! also it might seem like complicated & hard, but once you get the hang of it, its quite easy.
if you want to be making high quality gifs, i would look into getting photoshop. once you have photoshop and once you have found/made your gif you are going to want to sharpen it before anything (it just makes it look better…more sharp) once sharpened, you can then do what you please, you can colour your gif yourself, or you can download a psd, crop the gif, shorten it, put text on it whatever. once all is done, you will have to save your gif. if you want highest quality, be sure to make your gif suitable to the dimensions on tumblr (or else it’ll look grainy.)
other than using photoshop im not really sure how else you could make a gif at highest quality.
perhaps ill make a gif tutorial for y’all, that kinda goes more in depth? and will probably make more sense. - if any of you want that, im open to do that!