I need a knitting pattern?

so i am making a blanket for my bf. im making three long strips and im gonna sew them together instead of making little squares. well, the middle strip i made with size 6 needles and knitted one row them purled the other...i forgot what thats called. i got bigger needles for the two side (mainly to speed it up) i have size 15 and i think size 11. i was thinking about using the 15 and doing a garter stitch for the two sides. do you think this would look fine? im a beginner knitter so i think its pretty good for all that i know. the only thing i think might look weird is the variation in the stitching patterns. with it being garter, then the pretty one, then the garter again. i decided to do garter because its reinforced on the sides and doesnt curl up as much as the other one i am doing now. it rolls up alot so i wanted to do something different around the edges (reason for the garter) to keep it from rolling up...since this is a blanket, i dont think he'd like it rolled up! ha! and suggestions? or if you have a knitting pattern for the two sides please tell me!!!