You sure that’s 500000, and not 512000? 
As I can pretty much guarantee that one will work, and the other won’t! 
Another thing to be aware of is the question of whether the upload process on the Arduino IDE is actually running at that speed or not. As I know the esptool uploader on the esp8266 automatically reverted to 460800 if you try to specify a speed above that (not sure if it still does that or not)… perhaps the ESP32 uploader does the same… you have to check the output of the upload to see what speed it actually uses.
If you are ‘seeing gibbeish’ … you need to set the monitor_speed to the same as your Serial.begin() speed. If the upload is failing, you need to look factors such as is the upload_speed too fast for that board/your development environment, is the right COM port being used, is the cable/connector dodgy, and is the board resetting properly - sometimes the auto-reset is a bit dodgy.