Diamond isn't all that hard to get into. If i remember correctly, and i quote someone from the TL forums, "The difference between a 1700 diamond player and 800 diamond player is bigger than that off the 800 diamond player to a Rank 1 bronze player."

To get to diamond, i suggest that you learn a specific build order against each race and practice it to death. You can find stuff like these at TeamLiquid and Liquipedia. That alone should be anough to get you to diamond. Piece of cake

Sincerely, all the best dude.