I got this Body Solid curl bar. Works great, feels solid, haven’t had any issues with it so far.
I guess it depends on what your goals for a Gym are - I included the dumbbells because I like to do a fair amount of dumbbell exercises. If your goal is powerlifting you can obviously forgo them.
The barbell in the set I listed is fairly low quality, but that set is the cheapest way to get 300lbs of iron out there. If you want to throw up big numbers this isn't the barbell to do it on though.
The $500 in barbell/dumbbells/weights I listed could be spent alternately on a $125 CAP barbell that holds 1000lbs (cheapest I've found it), a $70 EZ curl bar, and $300 worth of plates off of Craigslist.
Those dumbbells you're talking about are awkward unless you buy mass quantities of 5s and 2.5s, so I wouldn't recommend them.
If it was me personally, I'd be torn between the initial setup I listed versus the decent barbell plus around 400lbs in iron, and the dumbbells - I would just save a little longer so I could afford all of it, but my budget has room for around $300 of irresponsible spending a month.