Summary:
The Spanish language can be learned in any order after getting to know the basic pronunciation, vocabulary and number study. It is actually similar when learning other foreign languages, not just the Spanish. Learning a foreign language, for one reason, requires curiosity and interest from the learner or the student because without the two, the lessons aid and memorization methods wouldn't have any purpose at all since it won't and can't be learned very well and put in to goo...
The Spanish language can be learned in any order after getting to know the basic pronunciation, vocabulary and number study. It is actually similar when learning other foreign languages, not just the Spanish. Learning a foreign language, for one reason, requires curiosity and interest from the learner or the student because without the two, the lessons aid and memorization methods wouldn't have any purpose at all since it won't and can't be learned very well and put in to good use by the student learning it. So why even bother?
Language also appeals to the personal interest of a person and one can't just be forced to learn it if the language doesn't shift the person's mood from boredom to excitement. In Spanish, it is important that you touch-base on specific lessons first which appeal to you the most because from there, other lessons of the Spanish language just easily flows in your system and before you even know it, everything you need to know about the Spanish language has already sink in.
What you may want to concentrate on is the Spanish verb conjugation because this is one area of the language which could become difficult for most beginners. Spanish verb conjugation could leave you with "how" and "why" questions but it could become a breeze once the lesson on the Spanish verb basic time frames has been focused to intently.
An important reminder in learning the language is to always keep yourself up to date with the lessons especially if you're learning from free online resources. There are always new approach and correction articles on past Spanish lessons so it's always a good idea to keep your mind open to possible changes since not all learning sources (especially if its free) are similar or accurate.
Another thing why learning the Spanish language can become as easy A, B, C is because the minute you progress on the different Spanish lessons over time, you also would have developed the adaptation of speaking and using Spanish in any way most comfortable for you and nobody has to correct you of your style!