You have done amazingly well, especially for a first-time project! Love your colors as well as the design. Yes, a walking foot is one thing that will be a huge help for this one and all future projects. I'd outline the chevrons with stitch in the ditch. Not sure what I'd do in the cream centers. An echo stitch might be an option or I like the suggestion of doing a simple tie there but recommend something such as pearl cotton or embroidery floss, even that skinny ribbon. Yarn is pretty before it's laundered but doesn't hold up well. As to basting. I use quilters' pins for mine. I have never used the spray but am told it can make a real mess of surfaces outside the edge of the quilt so be careful of that or put a sheet down--or take it outside . Again--great job with color choices and construction so far!