Play wbi. You get tons overtime, I try to get 10+ run each day since I play on my way to work/way back from work. 3 at the start of my trip,3 at the end of it. You get bios that set you up in the future for nat2 too
Go to your lab and use the item shop! Sometimes there will be packs of 25, 50, or 75 you can buy with gold or pink stuff. I've upgraded my shop to like Lvl 5 and it's pretty worth it. Send your guys on missions in the lab as well to rack up some Lab Tokens as well.