This is a very inexpensive machine, only $120 on Amazon, and the manual is
weak.

I'm teaching myself to do some work and having a hard time. It doesn't work
very well when I freehand attaching straps to fabric - can't make the fabric
feed sideways. Is making multiple "buttonholes" a good technique to form a
durable connection?

The material is denim or "duck" and the straps are nylon tubes so it means
going through 2 layers of each.

Would an embroidery foot enable me to feed the material from the left, right
as well as front and back?

http://www.singerco.com/accessories/...mbroidery-foot

Or

http://www.ebay.com/itm/Darning-Quil...-/370590539169