It's not necessary, no. Most people I know do their work in their rooms (so your desktop is fine) or at the library (which will have workstations anyway) and take paper notes in lectures, so you're at no disadvantage unless your course absolutely requires one
The only time a laptop might come in handy is around exam time, where library computers are snapped up by 6am, so you can work just at a desk or in an empty seminar room (this of course is only relevant if you work best in the library. Shouldn't be any problem if you can actually work properly at home)
You'll mostly be absolutely fine taking a desktop I personally only faced a couple of issues which was mainly group work where people wanted to meet up in local coffee shops etc or off campus. I found in this case I was not able to participate as much as I could in group meetings but otherwise I had no issues.
You don't need a laptop for Uni and I didn't have one last year however it did end up being a bit of a pain for me. People constantly wanted to work in each others rooms/common room where I either couldn't join or had them all in my room which wasn't the biggest.
There were also next to no free computers in library so working in there you needed a laptop and during nice weather people wanted to revise outside.
I ended up buying a laptop for next year because I decided the pros outweighed the cons for it, however if you're a big gamer maybe a desktop is the better option for you.
depending on your budget and how efficient you are at using it when building this desktop you could probably get a cheap (and I mean the cheapest lowest range) netbook on top of the desktop since as i understand it building computers usually works out cheaper than buying a standard one.
Get a desktop for gaming, Trust me. I bought a gaming laptop for uni and honestly I have never used it outside my room. Its just on my table all the time. You can easily just go to the library and use the workstations.
I had a laptop but rarely moved it from my desk..!
The main advantage of it however was that it was a lot easier than packing up a desktop computer every time I went back home for the hols, but if you're after a gaming desktop then I'm sure that won't put you off!
Well obviously , if you want to do all your work in your room and take notes on paper in lectures, get a desktop. If you want to take your laptop to lectures and the library, get a laptop.
I have a desktop and a netbook. I find that all the computers in the library are often taken, and it's much easier to just sit at a desk with my netbook than wait around for someone to leave (also I can then find a quieter space as computer areas are often noisy). The netbook is good because it's cheaper and smaller than a laptop, and all I really need in the library is microsoft word and the internet, and I had enough money for a decent PC and a netbook.
(It's much more expensive to get a laptop with the same spec as a PC. The money I saved by getting a PC left me enough to get a basic netbook as well!)
Get your gaming desktop if that is what you want. Be mindful of the fact you will need to pack it up and transport it at least 3 times a year if you are in halls. So consider the weight of your system.
Get a basic tablet or netbook/laptop to access google docs when you are out and about or collaborating with friends. It can be useful in lectures if the lecturer has posted the slides late and you have not had a chance to print them out.
I would definitely say build the custom desktop since you're into gaming. If you want something for general use like writing papers and looking up facts, get the laptop. I haven't checked prices for gaming in a while... But from what I remember, it's cheaper to get a gaming desktop than a gaming laptop.
I ended up with both. I got a desktop because I do a lot of digital artwork at home. However, I have a cheap, refurbished laptop I use when I'm studying on campus or when I need to bring up a quick video for my tutors. The portability of the laptop is nice, but I don't think I would call it a necessity. My laptop is currently sitting in a corner of my room and its cover is quite dusty. I think that's a good example of how much it's being used as opposed to my dust-free desktop system. Also an example of how badly I need to clean things around here.