Getting started:

Valve oil
Slide grease
cleaning kit
Starter booklet TC
Starter booklet BC trombone
Arban totally free and legal download:
pp1 - 56:
http://ffmrecords.com/wp-content/uploads/2017/10/39087017795040pp1-56.pdf
pp123 - 190:
http://ffmrecords.com/wp-content/uploads/2017/10/39087017795040pp123-190.pdf
pp283 - 347:
http://ffmrecords.com/wp-content/uploads/2017/10/39087017795040pp283-347.pdf