(If you prefer to work on your GIF on a different device than the one you used to video it, I suggest just uploading to Drive (you'll need to install the free Drive app). I've found that to be the fastest, easiest way to get media off of an iDevice and onto a desktop or laptop. You can download from Drive once you are on your laptop/desktop machine.)
Once I upload my video to ezgif, I can cut off any unwanted parts from the beginning or end of the video (if you don't want to cut anything, just be sure to play the video all the way through and set the "End time" by clicking "Use current position"). I can, also, do a number of additional things in EZGif such as crop, add text, speed up or slow it down (SUPER useful for all things physical!), etc. I, also, like this method because it allows you to video several actions at one time and then simply pull them apart once you upload the video. (Do be sure not to go too long because there is a file size upload limit. As you work with it you will learn how much you can do.)
If you give GIFFING a go and have any questions, feel free to contact me!