Really depends what you need to do. I can't say they're the most friendly programs for working with directly (they have rather intricate command line syntax), so I'd ask what exactly you're trying to accomplish. Since you have ffmpeg, I would presume you want video playback, editing or transcoding, and I would recommend you uninstall ffmpeg and use vmc (a graphical media player that forgoes ffmpeg for its own internal codecs) or use mpv
(it would appear mpv isn't in the mint repos and you'll have to settle for mplayer or mplayer2 instead), a console player that uses ffmpeg for its backend. As for image editing, it's between paint.net and the gimp. GIMP is more photoshop-like, but has a steep learning curve as a result and paint.net is for more casual use.
For my usage, I typically avoid explicitly installing things like ffmpeg and imagemagick and let them be marked as dependencies instead so that package management is easier for me overall, but that's just a clerical pet peeve of mine.
If you really want to try using these in the command line (I love the command line and I still avoid ffmpeg) then this is all the help I can give you. These can also be viewed on your machine by typing 'man ffmpeg', 'man imagemagick' and 'man gifsicle' in the terminal.
http://linux.die.net/man/1/gifsicleEdited by ZHoob2004 - 11/21/13 at 12:24am