One other tip...you can drop a mish once every eight days and have it autocomplete. This also is true for level 50s. Set up a scanner mish, talk to the scanner again, drop mish, instant profit. Not a whole lot, but every little bit helps
I thought it was 7 consecutive days....but I haven't had the need to Drop missions in a long time...
But ya, I've made the RWZ my new best friend. I been farming the same mission for a while now and I get anywhere from 3-5 Portals per run (On Rugged) with easy Minion defeats. One run can take less then 20 minutes and I net an easy 300k. Running the new TF also nets a huge profit. Since there are several Teams involved, I cannot actually Tank for my Team, we all just split up and help each Team out. So I run around with my AoE on and throw out my Ranged attacks, all the while swingin my Axe like a mad man. All in all, getting a few hits off here and there on any random Rikti will get my Team kill credit, and therefore extra inf/prestige/Merits. Now that's an easy way to net a good few mil in the time it takes to run it.
And just a quick response to the OP, I'm only about 15% into my 1 Billion Inf Badge, but I spent only about 27 Mil all together on the few IO's I have. Most of which actually went to the Crafting Badges. I maintain a 5 Mil range right now, I farm for an hour to get up as high as possible, check the AH for what I need and think is reasonably priced, buy or not, then start farming again.
-Taz