Ireal pro is a great tool, but:
1. The chords are all user-contributed and very often not great quality.
2. The midi backing tracks are awful, and I can hear their influence on a lot of jazz I seem to be hearing these days. It is often played much too fast and square.
£18 is pretty good value if you don't mind taking a tablet with you everywhere though.
I prefer the New Orleans Jambook. There are chords for each song and they're better quality. If you've never seen this kind of lead sheet the chords at the top are for instruments tuned in C, and the melody is for instruments in Bb. A great starting point! A great resource and all free.
https://cjam.lassecollin.se/