The fall colors like rust, mustard, olive and brown come in all price levels this season. I have found an ok quality of jeans (Universal Standard) and tank tops in mustard gold and a rusty color at Target. I think autumn colors for this year are the easiest way to go. You could just do tops in fall colors with your favorite jeans. I am looking for wide widths and high rises to look most current. Sneakers do not need to be expensive. Halogen and other inexpensive brands have those long cardigans that are popular now.. The Rack has lots of inexpensive tops and even teddy coats in fall colors.
ETA: I just noticed that you are in Germany, so this information may not be helpful. Just add a scarf in current fall earthtones and it will have a big impact.