Guilds: As soon as you can find one that will take you that is doing Heroic fights.
You want to have a 7* character so you can zone into a heroic raid w/ that one character just to get credit & start building up Shards of Han (or maybe even Gen.Kenobi)
Mods:
Do not farm the Battles for Mods. Just the 1 time to advance & that is it.
FARM mods from the Challenges Only.
Farm the Highest you can. So if its 5* Health but only 3* Speed, don't bother spending resources on the Speed Mods.
Don't bother Refreshing Green Energy till you get access to a Tier 3 Challenge for 5* Mods from good sets....
Offense, Defense, Crit Chance, Speed, & Potency are IMO the better more common sets.
Health, Tenacity, & Crit Damage are situational for only specific characters.
Pre-5* mods, sell all Greys except Arrows w/ Speed Primary & Triangles w/ Crit Damage Primary.
Anything that is Green+, Sell if you don't see Speed at L1 in the secondaries.
Don't try to level them, just sell them.
Mods are expensive to level & you'll get much better ones soon enough so you can afford to be picky about them.
You want mods that look good at L1 w/ Speed required & preferably some other good stats like Protection & Offense.
Your going to end up selling 90% of all the mods you farm at L1. Too expensive to gamble hoping a crappy starter improves till your years into the game & very rich.
Once you can summon good mod sets at Tier 5, then you start refreshing that Green energy when you can afford it & summon summon summon, just looking for the good starter mods & selling back 90% w/o leveling them.
Eventually you'll have a solid portfolio of mods, some will level up badly & you'll put those on lesser teams, others you'll get lucky & the leveling goes really well & gives you a shiny gem & you'll save those for top end Arena / Meta teams.