If you want to study the basics of law, where should you start?
Don't try memorizing individual laws. That would be a waste of energy, in part because --as you rightly point out-- laws change. There are many introductory books. Law 101, by Jay M. Feinman, is an excellent starting point.
The next step --broadly speaking-- consists of reading court decisions (aka court opinions). Opinions released by upper (aka reviewing) courts are available online for free. If you are interested in jurisdictions in the US, Leagle.com is one of many very good resources; EU cases are available here; and so forth.
Acquainting yourself with court opinions is quite beneficial. First, court opinions [collaterally] teach how to formulate one's legal positions. Rather than merely being formulaic and a copycat, a litigant is to convey that his legal position is more consistent (compared to the adversary) with the laws and underlying doctrines. His points are easier to get across by adapting his presentation thereof to how courts are used to handle the legal principles involved.
Second, court opinions identify the statutes that are relevant to the type of disputes that arise between parties. This is indicative of importance that a statute or procedural rule entails in relation to other laws.
Third, court opinions reflect how statutes, rules, and doctrines are interpreted. Oftentimes the way how legislation is worded leads "laypeople" to have misconceptions on the interpretation of laws and rules, when in reality these are construed usually in a much narrower way.
Law journals are a good source once you have gained some background in law and are interested in a sort of monograph about a topic that is new to you. But, as explained above, court opinions also serve that purpose (perhaps less scholarly).
Having a legal dictionary is always a good idea. Courts in the US oftentimes quote definitions from Black's Law Dictionary for crucial terms which statutory law does not define.
What is most applicable to real life?
Without knowing whether you are interested in a particular field, it is safe to say that contract law is the most applicable.
Entering contracts is part of our everyday life even if laypeople don't notice it when they purchase goods & services, reach an agreement, or engage in a course of conduct which reasonably fosters expectations. And good news is that the principles of contract law are largely similar among modern jurisdictions, including the America (the continent, not just the USA), many member states of the EU, and Asian countries.
The Restatement (Second) of Contracts is a very useful formulation of contract law. Courts in the US very often cite the Restatement for premising their decisions on contract disputes. In countries with a civil law system, the principles of contract law are usually formulated in one or multiple sections of the [countries'] Civil Code.
Procedural law (aka rules of criminal or civil procedure) is also highly applicable: Large portions thereof apply to all disputes which are brought to court. To a great extent these rules are very similar across the jurisdictions of one same country, but the litigant ought too ensure his compliance with the rules lest he loses the case for a technicality. Lastly, procedural law can be remarkably boring unless the person anticipates he will be involved in litigation.