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If you're serious about making gold through farming, then you're going to have food buffs up at all times, even in WvW. While gold find doesn't get applied to player kills in WvW, the magic find does. Also, magic find and gold find are added to your monster kills in WvW so that alone is a good reason to have it on.
How do you get great buffs for farming from food? You choose usually between the following bars:
The Omnomberry bar gives 30 magic find, 40 gold find, and 10 experience per kill.
The raspberry peach bar gives 26 magic find, 30 gold find, and 10 experience per kill.
Which is the smarter buy? I personally use raspberry peach bars over omnomberry bars. The 4% magic find and 10% gold find isn't worth it in WvW, and isn't that significant of an improvement to justify an extra 2 silver 12 copper investment per half hour. I'm quite content saving a little money and settling with the Raspberry Peach Bars.
Hint: Raspberries are a great item for flipping purposes!