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Swgoh farming flowchart

To give an idea of how things are prioritized, I looked at the various milestones/unlocks in the game, and weighed how easy they were to complete with how impactful they are to the current playing field. When doing so, the milestones break down as such:

1) Unlock Jedi Knight Revan. JKR and DR are gamechangers, especially if they are unlocked very early for new accounts.
2) Unlock Darth Revan, and consequently, Darth Malak. This is the first real challenge for the milestones, but with how impactful Sith Empire is in the Arena meta right now, getting these two unlocked as early as possible is key.
3) 7 star, G12+ the full Geonosian squad. Geos will handily finish the Padme event, and also contribute to your guild unlocking Wat Tambor shards.
4) 7 star and G12+ Separatist Droids AND Shaak Ti/501st. TB is the biggest event for overall progression to be measured, and these two squads are vital for both sides of GeoTB. Getting these early will be a huge boost for your guild.
5) Unlock Chewbacca and Han's Millenium Falcon
6) Unlock and 7-star C-3PO
7) 7-star Thrawn and Palpatine - This takes a Phoenix team for Thrawn, and the same team will make short work of the Palpatine event. Thrawn in particular is an incredibly versatile character that everyone should have in their roster, and built up.
8) Unlock and 7-star R2-D2, and then Commander Luke Skywalker.
9) Unlock BB-8 and Rey (Jedi Training). Not quite the dominant squad they were when RJT first hit the scene, They're still key for HSTR, and provide a consistent, reliable counter to Bossk squads in TW and GA. With episode 9 content incoming, they may get a big resurgence as well.
10) Unlock General Skywalker. He may be the newest, most badass event character in the game, but his requirements are very steep. As the meta reshapes, this milestone may move up in priority, but for now, each of the previous milestones plays specific, key roles toward guild contribution.
11) Unlock and 7 star Chimaera.
12) Finish up Separatists and helpful Galactic Republic characters, to further contribute to TB.
13) Finish up First Order and Resistance characters. This is a preemptive take, as we don't yet know how FO and Resistance reworks could change things with upcoming Episode 9 content. It's a safe bet that one or more of these characters will get a big overhaul, or other new characters make them more relevant.
14) Focus on the best "B" Teams, like Nightsisters, Triumvirate, and Imperial Troopers for roster depth.
15) Miscellaneous remaining characters and ships, weighted by usefulness. This section will be under constant review, and through feedback and research will shift pretty often.