Take your time, most new domainers register loads of domains and realise later the errors in most of the registrations.
Take 5 or 6 domains and make a start with them, learn the rights and the wrongs. When you have mastered them and understand more of the industry then go and bulk register domains.
Remember if they are free to reg now then they are likely to be free later.
The most common mistake is to grab loads of domains with great plans, test your ability first.
There will always be opportunities in this game, its like going to the fitness center for the first time, all eager and willing. 3 weeks later you have signed a contract for a year and never go again.
Start slowly is the best advice I can give you