Lens help? 90mm, 50mm or 35mm?

I have a Nikon D90 + 18-105mm kit lens, as well as a Tamron 90mm macro/portrait lens. With this in mind, would it be practical for me to get a 50mm lens?

The 50mm would be my multipurpose lens for shooting portraits, scenes, etc.cos I feel sometimes the depth of field in my kit lens is not enough. The thing I'm not sure is, what will the benefits of the 50mm be in daily situations compared to my 90mm? I don't see point in getting a 50mm if its going to produce the same results as my 90mm.

Alternatively, would it be better to get a 35mm since I saw somewhere 50mm is too narrow for crop bodies?

Also, I'm wondering if anyone knows if good fish eye adapters that can fit with my Tamron lens?

Personally, i have 2 50mm lenses and a 90mm macro lens…

really buying lenses really depends on your need… Or you end up with lenses coming out of your ears and never really using them…

as for fish eye adapters, don't waste your money…

Don't bother with fisheye adapters, none of them are any good. If you really want a fisheye, buy one of the manuals out there. Peleng makes one that I have for my Canon.

The 50 is going to be a lot different that then 90mm. The 50 is an excellent portrait lens. You can also purchase a zoom in the 28-70 range with f/2.8 as a walk around lens. It is not going to be as quite as sharp as the 50, but it will be a lot better than the kit lens and give you a lot of versatility. I have a Tokina which is quite nice.