I've heard of people having success taking a tablespoon of raw honey daily. It's supposed to be great for allergies.
Because fruit is high in sugar and sugar is pro-inflammatory, eat a variety of fruit but don't overdo it. The more important question is, what are you allergic to? Hard question to answer for those of us with a lot of allergies, and they are epidemic in the US probably due to our weird diets of processed foods and all the toxins we've added to the environment. When I grew up, everyone smoked, and all the kids had allergies and asthma -- not a coincidence. Now asthma is even worse, due mostly to the huge amount of carbon based fuel we burn. Meaning, there are a lot of anti-histamines out there, including freeze dried nettles, scutellaria, quercitin bromelain vitamin c combinations, homeopathic remedies, etc., but a cure is unlikely. The best you can do is control it by keeping your immune system from becoming overactive and avoiding inflammation -- sugar, simple carbs, and any foods you have trouble digesting, most commonly wheat and dairy but it could be anything, and keeping your air ducts clean and all that sort of thing. And some places are more allergenic than others.
Have you tried the Netty pot for your nose? As for "what is the best fruit to eat" All fruit is good
eat a variety of fruit