Cheespuffs has pretty much given all the suggestions you need but here's a few more:

-Races should be about moving as fast as you can, it is not an action map you try to complete as fast as you can.

-Races should not have a square shape, they should be round

-Instead of so many mines so close, you could simply put a lot less mines scattered all over the place and try it, to see if by keeping left held N dodges them all (see formica's "the crazy miner".

-Also, try seeing 'Geedy Sponzales' by invader for an idea of a good 'square-ish' race.

2.5/5 Too easy

Good Suggestions

1. Don't clump. You can get rid of the inside of the mine areas and just keep the boarders and it will still work fine, and there won't be as much lag.
2. Don't clump gold.
3. This race is made as if the user isn't that good at N. If you haven't already, try playing a lot of other racea and then make one, so you are better and can make it for those who are better. Why am I saying this? Because in the top left corner, when you jump from the tiles, you have to jump really short to not hit the mine roof. That's not what you want to do when making a race. This happens in other places where there is bad placement of gold where you have to jump a lot less.

Good luck!