I use Photoshop to make gifs. I don't know if you have it but that's the only thing I can think off for the moment.. You can go to File>Import Video Frames to Layers and that's when you can import your movie in. Once you feel that your movie is good, you go to File>Save for Web and Devices. This is when you can save is as a .gif
The file is too big? Are you planning to upload it on websites, for example Tumblr? I know that Tumblr doesn't allow any gifs bigger than 1 MB. In that case, you have to play around with the Ditter and Color Option when you save to webs and devices. You can also try this: Next to "Preset" there's an arrow. If you click on it and choose "Optimize to File Size and Set", PS will try to give you the best result it can within your MB limit. If it doesn't work, then you might have to resort to deleting frames or turning your whole GIF into greyscale.