you can do the same thing as gamer without welds if using pipe. i would suggest not having a front bar so you can sit under it though. to be honest, all you would need for tools is some way to cut the plywood (heck, many lumber stores often have a way to cut sheet goods for you to size) and a way to round the corners over.
you could also do the same thing with steel tubing, some premade angle braces you can buy and taping the holes then bolting it together. unistrut is a bit uglier but also works.
of course you could build it entirely out of plywood, use solid wood legs, etc. there are many designs you could go for. searching google for "computer desk", "diy computer desk" and "gaming desk" may give you some inspiration.
the most important features are always...
- if you intend to place the mouse or keyboard on top of the desk, having a relatively thin top is ideal. this gives you more leg room underneath without raising the level of your arms to use the mouse and keyboard.
- height should be within what your chair can adjust to for comfortable ergonomics. it is certainly possible to even make adjustable height legs if you wanted but is not really required.
- top should be large enough to give you plenty of space. how much you need varies on what you intend to put on the desk. if you want to keep the desk open you could always build some shelves up from it for speakers or other devices and use a monitor arm or shelf for the monitor. likewise, you could use a keyboard tray if you dont want to use the top of the desk. if you intend to put your tower somewhere else, think about having a shelf for it to keep it off the floor (so it doesnt such up dust from carpets,etc).
i'm using an old table i got for free from a retail store. its 3 x 7 so is more than large enough for my needs. all i needed to do was put new formica on the top which was fairly cheap. pictures in my signature if you care but its just a simple desk.