Depends on your definition of low spender, ICEx.

My definition of low spender is somebody that does jonin medal does monthly card and at most spends another 10$ per month in the game, so 20-25$ per month at most.

What is your definition?

There's no country where 75$ per month is considered a low quantity by the average person that walks in the street, but there are quite a lot, overall in the hk timezone, where they are a quite high quantity.

Stacking is simply not worth it if you get less than 15/20k coupons+ingots per month.

The usual f2p or low casher cannot stack at all his move 1 except for refinements because is not worth it. It is useless to get a 35k power move 1 while leaving move 2-4 to 20k. You will continue to lose to people that did not do like you and spreaded the things, getting one 30k move 1 and 3 25k move 2-4. You begin to get a significative advantage when your move 1 ninja reaches 40-45k over who did not stack, but as i said that thing is not achievable by f2p and low cashers without leaving in the meanwhile move 2-4 at 20k power. That means you get still owned by somebody that did not do like you and spreaded more the resources, ooverall because to take advantage of an high stacked move 1 you need p2w ninjas like itachi susano or naruto ninetails chakra or very hard to get ninjas like kurama naruto.