Best way to farm gear?

Don't do multi sim beyond two at a time. That being said blue and purple gear does not drop at the normal 33% average. Not sure about blue but purples have a 10% drop rate. Meaning you only get one or two using your entire energy bar on average. And as so gear takes 50 pieces it can take two weeks for a single piece of gear at level 9 or higher. And raid gear even longer dependibg on how often your guild runs them and what it drops for you. Raids drops have a nasty habit like guild store, where they drop a crutial gear upto just short of unlocking the start dropping others. And your chances of getting them from the gear packs does not justify the cost.

Always buy all the gear you find in the store (for credits, like 800 - 2100). All 4 of them, 4 times a day. Even the ones you already have hundreds of (chances are you'll need thousands of them in the end).