wait until efs has a sale on bands and get a mini, monster mini a light and an average. They occasionally have a sale where the more you buy the bigger % you get off.
Either that or look into iron woody assisted pull up packages.
with all those exercises it's hard to say one particular band is the one you need.
I like minis/monster minis for pull aparts and average for pushdowns and higher rep assisted pullups (I suck at pullups I can only do 4-5 deadhang pullups for 3-5 sets)