Reducing caloric intake will be superior in weight reduction than doing cardio IMO. Go to any gym and look at the treadmill section and you will see that's where the majority of fatties are located. So your diet needs to be the priority if you want to see your abdominal section.

Building muscle is not rocket science, design a weight lifting program that challenges you, make sure you hit each body part, progress over time, and allow for rest and recovery in between sessions.

Im not sure I understand what you mean by "looking skinny" as the fastest way to look like you have gained 10 lbs of muscles is to lose 10 lbs of fat. Ive seen plenty of "skinny" guys that weight 170lbs that look like they are 200 because they are shredded and ripped.