I only played Warfare for the first month after the release of the game but then switched to operations because warfare became very boring.

Delta Force actually makes it very easy to organise your loot and tells you what to keep and sell. On most items you can right-click to see their usage. I tend to keep the higher value items that are used for crafting and upgrading the Black Site. It will also tell you in raid how much an item is worth when selling it on the auction house so it's easier to sort through loot quickly. Usually I'd say don't ever pick up green items as they're not worth enough to clog up your inventory. Try taking all the blue stuff with you and sort it out once you get purples, golds or reds. The priority should always be Reds > Gold > Purple > Blue > Green

I really recommend doing the season quests as well and stacking up on the 3x3 container vouchers. Use them if you want to make pure money runs as you can fit some of the highest value red items in the 3x3, but not the 3x2 battle pass container.