Once the concept is studied i think students have to try the problems in the respective concept so that he concept will be more understanding and interesting...one can suggest herstein or fraleigh for the reference

If you approach Algebra in the proper way, that is through number theory,  I feel there is no room for any difficulty  if you follow the usual rule of study maths that is learning  by doing.

If any student feels any difficulty in Algebra it is because of the way they approx the subject or rather the wrong way the subject was introduced to them