500 euro is really nothing, in the best case you could have a really small 2d prototype for that amount. Then you could use that to try to generate some money and flesh it in a proper game. If the game is then very successful you can invest the money to make a 3d game. If instead money earned is small, make another 2d game of better quality and keep doing that since you get something that can generate some money to pay for the 3d game.