Well done and grats, that's a super first project!!
It took me years to get that final seam down. I'll have to take pictures next time I do one.
Some people don't need a lot of space to work with, I need at least 1 foot total (six inches each side) myself. So I put on the binding first on the top of the quilt, I use the french double fold technique so have the rough edges all to the outside on the top, sew around and miter my corners. First I make sure my end is cut at the right angle, and I start in the middle of one of the long sides, leaving about that 6-8" tail. I miter the corners. When I come to the meeting point, again I stop sewing about 6 inches shorter than I want. I unfold the binding and lay the ends over each other, using a pencil to draw the angle from that end I made sure was correct.
Here's the slightly tricky part, you cut 1/2" further (extra, remember extra for the seam!) towards the end of the binding from where you drew your line because that is your seam allowance (1/4" from each side). If you cut the wrong way, well, all is not lost, you just put another piece in, line it up again, and trim down. But if you do it correctly, your binding will be perfect each time.
After you sew the seam, refold your binding, sew that final foot of seam, flip to the back and my prefered treatment is hand blind stitch down.