The Game Changers have farming guide videos on youtube. You can find the current Game Changer Beginner advice videos here:
https://forums.galaxy-of-heroes.starwars.ea.com/discussion/154847/new-player-farming-guide-2018#latest
Scoundrels are a good thing to farm, as they are needed for credit heist and training droid heist. Stormtrooper Han is good to farm as he is both a rebel and a scoundrel, so he is multipurpose. If you already have Phoenix squad almost at 5, it may be best to finish them to 7* as you can use them for events to get Emperor Palpatine, Grand Admiral Thrawn, and later, Chimaera (Thawn's capital ship) if you also farm the phoenix ships.
I have prepared an index of reoccurring events for new players, which includes listing the characters needed for each event as well as suggested level and gear level that may be helpful when planning what to farm.
https://forums.galaxy-of-heroes.starwars.ea.com/discussion/154696/reoccurring-events-and-characters-required-index/p1?new=1
I also have an index of terms and acronyms in case any you need it, as people generally use a bunch when giving advice. https://forums.galaxy-of-heroes.starwars.ea.com/discussion/154048/guide-to-the-acronyms-and-terms-of-star-wars-galaxy-of-heroes-swgoh#latest
Hope this helps!
