The reason why nobody helps much here is because you're asking at the wrong place. This is where players leave an introduction about themselves so that others can know about you, so nobody is expecting questions on the introduction forum. For getting more information, there's a question & awnser thread in the game discussion forums. You can also start a thread there, stating your questions. Some help, others give tips.
For more tips on fantasica and such, check Fantasica Encyclopedia. Most of the general wisdom is located there.
And regarding those cards with defense stats only - they are "monsters", which behave differently from your units.
Regarding enhancing, i'll gave you a practice tip: 2 star units/monsters give more enhance experience when you enhance them with 3 1 star cards (to reach level 4) , and 3 star cards are most optimal with 16 1 star cards (to reach lvl 10). You'll find the reason of these numbers as you travel for knowledge.