You get 3% Attack and Defense the first reset 3% Spy A and D the next 5% A and D the third 5% Spy A and D the fourth A bonus of 50 ally slots for every reset too, but items for only the first 4. High lands complete gives four resets.
There are 4 reset items but you only get credited for 2 resets if you reset at hlbc. Best to do 4 resets at 25lands