How can I inexpensively replace my vertical blinds with something that looks professional?---I can sew.
Flat bed sheets work well for fabric, however, depending on how much space needs covering it might be more than you want to pay. Sheets can get pricey. A very inexpensive option is drop cloths. It sounded kind of crazy to me at first, but check out the link and it may give you some further ideas. Please post some after pictures as we'd love to see them. Good luck!
DIY Roman Blind - https://www.hometalk.com/26788580/sew-a-diy-roman-shade?expand_all_questions=1
DIY Drapes from Drop Cloth - https://www.hometalk.com/5200175/diy-curtains-no-sew-canvas-drop-cloth?expand_all_questions=1
Ikea sells inexpensive draperies of various fabrics and lengths, which you can then easily hem to your required length.
Roman blind is a good option. Easy to make also. Look on Pinterest for instructions.