www.learnjazzstandards.com/
learn jazz standards is a great website which includes many jazz standards used for auditions and competitions around the world. Each standard comes with backing tracks to play along with, as well as recordings of the original artists (which all jazz musicians should be aiming to emulate).

www.musictheory.net/lessons

musictheory.net provides basic theory knowledge all the way up to University level understanding.

www.imusic-school.com/en/tools/online-metronome/
A metronome! To help you keep time....which is important...like really important...