First try at modding; I see this map is short, so I think that's a good place for me to start.
Easy
0:12.685: This slider should probably be a tad further away from the end of the previous one.
0:14.024: Move this a bit to the left.
0:15.364: Too far from the previous circle. Two possible solutions here: reorient the slider or reposition it.
0:18.043: I'd put this a bit farther down.
0:19.383: Move down to the same horizontal level you moved the previous note to, and move it to the left.
0:23.402: End your spinner here. That makes it a bit short, I know, but that way it will last a proper number of beats. That, or add another 4 beats to the spinner if you can.
Normal
0:10.673: (1) Too close to the end of the slider that comes before it.
0:12.348: (3) Unless you intended to do this on purpose, it is too far from where the (2) slider ends.
0:13.018: (2) Too far from the end of the (1) slider.
0:13.688: (4) ^ Same thing ^
0:19.718: (2) I'd put this a bit closer to the end of the (1) slider.
0:20.723: (1) Too far from the end of the previous combo's slider.
0:23.402: (Sp) Same solution as Easy.
Insane
0:07.449: (2) You really shouldn't do this. The spacing between the end of this slider and the next (3) note will confuse people. Fix this.
0:09.836: (1) Moving this down two grid notches will result in happiness.
0:11.469: (2) First item I listed for Insane, you did it again here! Fix it here somehow too.
0:15.489: (2) Again! FIX IT!!
0:18.169: (2) I will not have these twos prancing about incorrectly all day! FIX THIS!!!
0:20.514: (9) Move this down as I described in the 0:09.836 entry.
0:23.402: (Sp) Same thing as Easy/Normal.
Edit: Also, you can't manually add the Skip button; it will add itself automatically when someone plays it if there's enough intro time before the beginning of the song.