Advice for my first build...

Because he's on a budget and it's an option to widen the chances of getting cheaper wheels. It's just advice and options.
As you're not actually supplying advice or help I suggest you go to the angry-man thread and shout there instead.
If you don't have anything nice to say.......

I was offering advice.

What 126mm wheel would you suggest he go for on a newly spaced track frame that more than likely doesn't have drilling for a rear brake?

Track wheels come up on here for under £100 frequently with fairly good spec open pro/sport on fixed/free hubs.