The machine I use - my grandmother's Singer 15-91 (circa 1948) - can only do straight stitches. Good thing that's all you need (00), except if you want to do some basting (06). Rather than baste, I typically use a flat felled seam or just roll a hem to cover any ragged ends.
As everyone else suggested, start with some cheaper fabric, like 1.9oz. You can get it @ Joanns for around $7/yd - they call it "utility fabric". You can sew all day long on this stuff, learning some various tips & techniques.
When you feel you're ready, you can make a tarp out of 1.3 sil and/or a quilt/bag out of .9 or 1.1 (OWF, Quest, TH, et al). Ironically, the packs I make use good ole' Joanns 1.9.