When I wanted to have wavy hair I'd put some Tresemme non-hardening gel and braid my hair while it was wet and then sleep that way. Then in the morning I'd simply take the braids out and fluff out my hair. It worked great for me.
Try sleeping with wet hair and put your hair in two plaits..It makes it kind of crimped and wavy. Or of you can afford it, buy some curling tongs. There are some that aren't too expensive but work well :)
GET SOME JELL ANY KIND AND PUT IN HAIR.THEN GET A TOWEL MAEK IT HOT THEN RING IT GOOD.LEAVE ON HEAD FOR 1-2 MIN SO MELT JELL IN HAIR.THEN BRUSH IN DESIRE FORM THEN PUT WAVES CAP ON OVA NIGHT AND REPEAT STEP
u should get a curlier. Then you can curl your hair and then when you wash it it can be straight again.