should i waste my apples?

If you're aiming for prisms and MLB Chaldea Lunchtime (if you don't have it already), then save at least golden apples for lottery. If you're not, then you can clear out the shop for all the materials you need with the use of apples if you like. But lottery is kinda good place to get some valuables, like gems for skills, qp, friend points, some ascend materials, so some golden apples are always nice to have. If I were you I will prioritize what I need the most. And also 10 hearts will be available in the shop on second Christmas Lottery in case you won't get all needed.

Lotteries are more generous than normal events. And we still have 9 days of the Halloween event to farm with natural AP. I would save your apples for Christmas events unless you get to the end of this event and really need to get xx material that won't be in the Christmas events or that you need to level up a servant for the events.

If the materials in this event are actually ones that you need right now, then it's really not accurate to call it a "waste" of apples. You should probably try to at least grab the materials that you need right now. Nothing sucks worse than getting a 1/2 AP Ember Gathering week, or a lottery that throws endless exp cards at you, when you lack sufficient materials to ascend the servants that you actually want to build.