Get Rid of Your Blues
When you reach level 30, chances are, you’ll still be decked out in a bunch of blue gear. Before you hit the Dark Zone, you’ll want to replace these with better purple gear at least. Thankfully, The Division does give you a couple of fairly reliable ways of farming for purple gear.
Firstly, you can run the final story mission, General Assembly, multiple times. If you run the mission on hard mode, you’ll be rewarded with a good amount of purple gear each time you complete the mission. Continue this process until you find enough decent purple gear to replace all of your blues.
After hitting level 30, you’ll also be able to tackle daily hard mode missions. Your goal here isn’t to farm for purple gear, but rather, to get Phoenix Credits so you can purchase Superior (and High-End) blueprints from special vendors. You’ll also get purple drops from running the hard mode dailies, but General Assembly’s your best bet if you’re just focusing on replacing the blues.