With regards to the credit issue I had to switch from small guild barely doing a raid every couple of weeks to a bigger more active guild doing raids every 3-4 days. Really helps, even just joining and not doing any damage yields a sizeable amount of credits.
I'm level 75. Good news is levelling slows down A LOT, you can play catch up and not worry about getting your toons up much above 70 for a while.
Depending where your guilds at with raids you may want to knock out at least one 7* just so you can post a no damage on a heroic or high tier raid.
Like everybody else said though just focus on one faction. Synergy really goes a long way, it's why Phoenix are so common around mid to late game. Plus they fill in a few legendary requirements. Might be a bit late to start a fresh farm on those for now.
Oh and you'll need millions just for 5 dot mods as well. Those are really expensive to max out. I still haven't done most of mine.
