The best books for beginners are Genki I and Genki II, no question.
Phone apps:
- jisho.org
- Google Translate
- Kanji Study
- Tango Risto
If you can read hiragana/katakana fluently, feel free to try my Konna Kanji app as a Kanji reading quiz/practice tool that I made some time ago. JLPT N5 is your starting point.