There are many ways to increase your core strength that will help you with more advanced skills.
Check out the exercises in our article 6 core strength exercises that are better than crunches. The routine includes videos and tutorials so you'll be able to jump right in! It also goes into determining why you want a strong core and different ways you can reach your goals.
If you want a real core challenge than the L-sit is a great whole body strengthening exercise that will require a ton of core strength. This article shows you the progressions you can work through to develop this move and impress your friends! :)