Completely based around messing with the player. The last gym is gonna have a decoy gym leader with 6 magicarps. Then the real gym leader pops out and has an amazing like smogon level team. My buddy who's mappingalready has 3 towns done.
Gimp doesn't export animations very happily. Your best bet is to open the GIF in Photoshop and then Save to Web. Download Photoshop CC, the trial is free :)
We have our own server we use for the trading- we're not using an online one. While it does require maintenance, its on the whole better because its a lot more customizable and so on.