Do i really need and electro-static discharge strap when assembling a pc or does it not make much of a difference
I would say USE one, its generally a good practice to wear a strap and they can be had for pretty cheap
if its convenient for you to get, but otherwise you needn't worry.
I've never used one and I haven't broken anything yet.
At the same time though I make sure to tough something that is grounded frequently while building.
when the psu is plugged into the wall and you touch the pc case/psu enclosure, it will do the same as a esd strap, the enclosure is earthed in every psu i have pulled apart.