In Candy Crush Saga level 500 you need to bring down the ingredients and score 80,000 points to complete the level. You will need to remove the cake bombs and blockers to be able to succeed at this level. The cake bombs will help with the blockers, so try to clear these as soon as possible. Try to avoid releasing the bombs as long as possible by leaving the locked candy below it for as long as possible. The bombs do not fall that frequently though so do not tend to be too much of a problem. The real problem on level 500 is getting rid of the blockers once you have got rid of the cake bombs (assuming you have!) As the ingredients tend to be settled on top of the blockers, the only choice is to make special candies but because they are positioned in the bottom corner the special candies need to be at the bottom or sides of the board, which is the hardest place to make them. Some players recommend only unlocking the ingredient makers on one side of the board. Then you only have to work one side of the board.
Level 500 is difficult and so you will have to be patient and wait for a good board. Keep making lots of special candies and this should help. You may find that the special candy boosters might be useful on level 500, as might extra moves. Lollipop hammers could also be good if you have just a few moves left and no other chance of winning.