First
s that you have decided to sell your collection. I know that feeling about real life taking priority - it doesnt make it any easier but at least if you sell on here you know they are going to great collectors. I hope you manage to keep your favourites.
The easiest way to sell anything online = fantastic pictures!
As Eternia says many G3s price themselves anywhere from $2-5 with most hovering in the middle of that. I would offer them initially individually but sometimes you will find G3s sell better if you can offer price deals or even groups of them at better prices. But try one by one at the start as you never know who is looking for what.
It depends on how many you have for sale as to how you list them. I have always found that pictures rather than a list of ponies will get the most attention. But if you have lots and lots of ponies, for ease you may be best picturing batches of ponies and then listing others you have available; gradually take more pictures and replace the list with more images.