500 can get a nice bike depending on what you plan on riding. I ride cross country trails and my 500 dollar bike doesn't limit me in anyway where I ride. I also suggest that you learn to fix things on your bike. Check ebay for parts and you can probably get them fairly cheaply. RJ the bike guy does videos on bike maintenance that are helpful. a new derailleur chain ring and chain you can find a way to get for around 100 and is easy to replace yourself. Upside for getting a new bike is getting disk brakes I find them better than rim brakes. I have a '18 Fuji Nevada 1.7 29er it was an improvement over my '90 Fuji thrill. Check out local bike shops if you decide to look for a new bike they can steer you in the way of a new bike for your budget.