The key to exercise is that you do not need elaborate equipment. You just need some creativity and discipline to stick to living a healthy lifestyle. That said, skateboard can be a very good tool for exercise. Why do you need to buy the ab roller when you have a skateboard? The function of both the skateboard and the ab roller is the same. They are different names and forms but they can be used for same function that is to increase core strength that is the ab as well as for aerobic exercise.
Now if you don't have the board, you can always do pushups. The key is to do the right form and to keep up with it. When you first start out, you won't be able to do much but don't give up. Even small increment of improvement will add up over time to help you have more energy, live more healthy and also to look good. Don't do it for anyone else but for yourself. Last but not least, not all of us can have a six packs and you don't have to. It's important to stay healthy and to love as well as to appreciate yourself. If you don't love yourself, how can you expect the world to love you right? Truth is relative. There is no wrong answer here.