We totally know the budget struggle when it comes to running and finding a decent pair of running shoes that fit your budget. However, it is almost a complete necessity that you have decent running shoes - especially if you are running multiple times a day or each week. If you do not wear the right shoes, you could potentially face some serious injuries and develop bad running habits and patterns that lead to prolonged and chronic injuries over time.
First off, if you do not have a good pair of running shoes that have enough cushioning and support built into the soles, then the bottoms of your feet will start to ache, and you might be deterred from doing other tasks that you want or need to. Even simple things like walking or standing might become painful. In some extreme instances, the bottoms of your feet might even bruise. You may also strain your fascia, a tendon that runs along the bottom of your arches and helps to absorb the impact and shock of running. This can lead to some very painful runs, intense swelling, and having to take off from running completely for several weeks or months to let it heal.
If your running shoes do not offer supportive ankles or a high enough "lip" around the ankle, then you might be at risk at over or under-pronating, mean your ankles turn outward or inward on themselves. This can become painful, and cause you to put weight on the insides or outsides of your shins and knees, which can cause problems down the road.
Finally, running shoes just help you to be a better runner. They help you perform better, run faster, and develop a more efficient foot turnover and foot strike. If you are looking to not just enjoy your runs pain free, but actually develop yourself as a decent runner and decrease your running paces and times, then investing in a good pair of running shoes is worth it. Plus, you will be happy to hear that good shoes will last you quite a while! You can wear your running shoes anywhere from 300 to 500 miles before you have to swap them out.