1. Number of frames. If you put many frames in one gif, it will pass the limit. It depens on the size of the gif. For example, a gif of 500px won’t let you put many frames (moreless 10), but a gif of 160x160px will let you put 40 frames or even more. Gifs of 245px will let you put moreless 30 frames. It also depens on the width. Resume: the bigger the gif, the less frames it’ll let you put.
2. Size of the gif. Big gifs will always weigh more than small gifs.
3. The coloring. The coloring has influence too. If the psd you use has a lot of layers, your gif will weigh more. Black&white gradient maps will add a lot of weight (between 100kb and 200kb). Also, if the coloring you are using adds many colors to the gif, it will weigh more.
4. Save settings. Take a look to this.
“From the day they arrive on the planet, and blinking step into the sun, there is more to see than can ever be seen, more to do than no, hold on… sorry, that’s The Lion King.”