Originally Posted by: GielPetI am very pleased with Guitartricks, very good lessons, good instructors, good content all.[/quote]
Good to hear!
[QUOTE=GielPet]The problem I am facing is how to determine my level of skill, when should I practice more on a certain skill or when is it enough to move to a next challenge.

If you have not yet, I encourage you to go through Guitar Fundamentals 1 & 2. That way you can learn or firm up your basic skills & knowledge.

http://www.guitartricks.com/course.php?input=1
http://www.guitartricks.com/course.php?input=2

After that pick a Style Course (Rock, Blues, Country).

http://www.guitartricks.com/course.php?input=rock1
http://www.guitartricks.com/course.php?input=blues1
http://www.guitartricks.com/course.php?input=country1

All of these are designed with the premise "if you can do this, move forward" curriculum in mind. So you can confidently use those courses, learn the skill or knowledge presented in each lesson, and then click the next button to learn more! Every lesson in all the courses build on previous lessons.

Beyond that, and most importantly, what are your goals with the guitar? If you can clarify what you are after I am sure we can point you in the right direction.