Quranic Arabic 

If you are interested in this topic ... 

Here are some steps. 

1. Learn Arabic slowly by natural osmosis. Learn Quranic Arabic word by word. quranwbw
2. Learn the Arabic alphabet. There are several ways. Not too hard. Use google for leads. Pretty easy - should not take over a week. Don't put it off.
3. (After learning the alphabet) Build a Quranic vocabulary 10 words/day over 1-2 years. Use these two tips to help A) Learn words using word frequency analysis to prioritize learning more frequent Quranic words first. (Good for motivation.) B) Use a scientific memory technique (spaced repetition system) to enhance adding new words to memory. See this memrise resource (daily use.)
4. (A few months into, or concurrently with, with previous memrise step) take an Arabic grammar (nahw) / morphology (sarf) course. Bayyinah TV has a good course (e.g. "dream.")  In particular, an understanding of the basic rules of sarf (morphology) and verb conjugation makes expanding one's vocabulary much easier.  
5. Use corpus.quran.com for Quranic grammar (and its associated Quran dictionary for search and morphology) to help further develop your skills

Note: If you are interested in Arabic outside the Quran

• Later on, if you are interested in  hadith / tafsir in Arabic you should learn to read Arabic without diacritical marks (like native Arabs).   Bayyinah TV's "Reading the classics" and/or software to add Arabic diacritical marks might be helpful. Knowing sarf (morphology), nahw (grammar), vocabulary, verb conjugation, or general familiarity with Arabic and practice will make this much easier. Tipsheet.
• If you are interested in understanding / speaking  Arabic  with Arabs (and other activities) the following might be helpful: 1)  watching tv in Arabic, 2) Pimsleur - which has a monthly subsciption, 3) talking with Arab speakers.       You can use "Google Translate" on your phone the "conversation" button to help.    If you need to understand a simple sign or book passage you can try to use google's Augmented Reality feature in your phone's camera (e.g. "camera" icon in "google translate" on your phone).     (Sometimes, these steps may have somwhat limited use for learning to read and understand your Quran in Arabic. ) 
• Chrome browsers have a handy feature - just click a button to use machine translation to get the gist of the website page one is looking at in your language.
• Learn to type in Arabic. 1)  find out how to add Arabic to your computer. 2) Add a "on screen keyboard" icon to your task bar at the beginning  3) Later learn touch typing in Arabic 4) Look into adding Arabic fonts like "KFGQPC HAFS Uthmanic Script" and "KFGQPC Uthman Taha Naskh" 

Finally, how long does it take to learn a language? Depends. If you are trying to learn a language similar to English like Spanish or Portuguese, much faster. A significantly different language like Arabic or Japanese, much longer. For Arabic , probably 1-3 years with a very significant time investment during this period -depending on effort, natual language ability and level desired (possibly 2200 hours for "professional working" proficiency?). Given the effort required, one might want to first establish the basics.

For example:

• a solid foundation of prayers
• Quran (read cover to cover the meaning in English at least twice)
• familiarity with the life and example of prophet Muhammad
• good, knowledgeable, practising Muslim friend(s)